is included in the section entitled ``GNU Free Documentation License''.
(a) The FSF's Back-Cover Text is: ``You have the freedom to copy and
-modify this GNU manual. Buying copies from the FSF supports it in
-developing GNU and promoting software freedom.''
+modify this GNU manual.''
@end quotation
@end copying
@end ifnottex
@menu
-* Overview:: Basics, usage, etc.
-* Program Structure:: Arglists, @code{cl-eval-when}, @code{defalias}.
-* Predicates:: @code{cl-typep} and @code{cl-equalp}.
-* Control Structure:: @code{cl-do}, @code{cl-loop}, etc.
-* Macros:: Destructuring, @code{cl-define-compiler-macro}.
+* Overview:: Basics, usage, organization, naming conventions.
+* Program Structure:: Arglists, @code{cl-eval-when}.
+* Predicates:: Type predicates and equality predicates.
+* Control Structure:: Assignment, conditionals, blocks, looping.
+* Macros:: Destructuring, compiler macros.
* Declarations:: @code{cl-proclaim}, @code{cl-declare}, etc.
-* Symbols:: Property lists, @code{cl-gensym}.
+* Symbols:: Property lists, creating symbols.
* Numbers:: Predicates, functions, random numbers.
* Sequences:: Mapping, functions, searching, sorting.
-* Lists:: @code{cl-caddr}, @code{cl-sublis}, @code{cl-member}, @code{cl-assoc}, etc.
+* Lists:: Functions, substitution, sets, associations.
* Structures:: @code{cl-defstruct}.
-* Assertions:: @code{cl-check-type}, @code{cl-assert}.
-
-* Efficiency Concerns:: Hints and techniques.
-* Common Lisp Compatibility:: All known differences with Steele.
-* Porting Common Lisp:: Hints for porting Common Lisp code.
+* Assertions:: Assertions and type checking.
+Appendices
+* Efficiency Concerns:: Hints and techniques.
+* Common Lisp Compatibility:: All known differences with Steele.
+* Porting Common Lisp:: Hints for porting Common Lisp code.
+* Obsolete Features:: Obsolete features.
* GNU Free Documentation License:: The license for this documentation.
-* Function Index::
-* Variable Index::
+
+Indexes
+* Function Index:: An entry for each documented function.
+* Variable Index:: An entry for each documented variable.
@end menu
@node Overview
they write have grown more ambitious, it has become clear that Emacs
Lisp could benefit from many of the conveniences of Common Lisp.
-The @code{CL} package adds a number of Common Lisp functions and
+The @dfn{CL} package adds a number of Common Lisp functions and
control structures to Emacs Lisp. While not a 100% complete
-implementation of Common Lisp, @code{CL} adds enough functionality
+implementation of Common Lisp, it adds enough functionality
to make Emacs Lisp programming significantly more convenient.
Some Common Lisp features have been omitted from this package
@item
Some features are too complex or bulky relative to their benefit
to Emacs Lisp programmers. CLOS and Common Lisp streams are fine
-examples of this group.
+examples of this group. (The separate package EIEIO implements
+a subset of CLOS functionality. @xref{Top, , Introduction, eieio, EIEIO}.)
@item
Other features cannot be implemented without modification to the
Emacs Lisp interpreter itself, such as multiple return values,
case-insensitive symbols, and complex numbers.
-The @code{CL} package generally makes no attempt to emulate these
-features.
+This package generally makes no attempt to emulate these features.
@end itemize
file @file{cl-lib.el} and rationalized the namespace for Emacs 24.3.
@menu
-* Usage:: How to use the CL package.
+* Usage:: How to use this package.
* Organization:: The package's component files.
-* Naming Conventions:: Notes on CL function names.
+* Naming Conventions:: Notes on function names.
@end menu
@node Usage
@section Usage
@noindent
-The @code{CL} package is distributed with Emacs, so there is no need
+This package is distributed with Emacs, so there is no need
to install any additional files in order to start using it. Lisp code
-that uses features from the @code{CL} package should simply include at
+that uses features from this package should simply include at
the beginning:
@example
@noindent
You may wish to add such a statement to your init file, if you
-make frequent use of CL features.
+make frequent use of features from this package.
@node Organization
@section Organization
will take care of pulling in the other files when they are
needed.
-There is another file, @file{cl.el}, which was the main entry point
-to the CL package prior to Emacs 24.3. Nowadays, it is replaced
-by @file{cl-lib.el}. The two provide the same features, but use
-different function names (in fact, @file{cl.el} just defines aliases
-to the @file{cl-lib.el} definitions). In particular, the old @file{cl.el}
-does not use a clean namespace. For this reason, Emacs has a policy
-that packages distributed with Emacs must not load @code{cl} at run time.
-(It is ok for them to load @code{cl} at @emph{compile} time, with
-@code{eval-when-compile}, and use the macros it provides.) There is
-no such restriction on the use of @code{cl-lib}. New code should use
-@code{cl-lib} rather than @code{cl}. @xref{Naming Conventions}.
+There is another file, @file{cl.el}, which was the main entry point to
+this package prior to Emacs 24.3. Nowadays, it is replaced by
+@file{cl-lib.el}. The two provide the same features (in most cases),
+but use different function names (in fact, @file{cl.el} mainly just
+defines aliases to the @file{cl-lib.el} definitions). Where
+@file{cl-lib.el} defines a function called, for example,
+@code{cl-incf}, @file{cl.el} uses the same name but without the
+@samp{cl-} prefix, e.g., @code{incf} in this example. There are a few
+exceptions to this. First, functions such as @code{cl-defun} where
+the unprefixed version was already used for a standard Emacs Lisp
+function. In such cases, the @file{cl.el} version adds a @samp{*}
+suffix, e.g., @code{defun*}. Second, there are some obsolete features
+that are only implemented in @file{cl.el}, not in @file{cl-lib.el},
+because they are replaced by other standard Emacs Lisp features.
+Finally, in a very few cases the old @file{cl.el} versions do not
+behave in exactly the same way as the @file{cl-lib.el} versions.
+@xref{Obsolete Features}.
+@c There is also cl-mapc, which was called cl-mapc even before cl-lib.el.
+@c But not autoloaded, so maybe not much used?
+
+Since the old @file{cl.el} does not use a clean namespace, Emacs has a
+policy that packages distributed with Emacs must not load @code{cl} at
+run time. (It is ok for them to load @code{cl} at @emph{compile}
+time, with @code{eval-when-compile}, and use the macros it provides.)
+There is no such restriction on the use of @code{cl-lib}. New code
+should use @code{cl-lib} rather than @code{cl}.
There is one more file, @file{cl-compat.el}, which defines some
-routines from the older Quiroz CL package that are not otherwise
+routines from the older Quiroz @file{cl.el} package that are not otherwise
present in the new package. This file is obsolete and should not be
used in new code.
Internal function and variable names in the package are prefixed
by @code{cl--}. Here is a complete list of functions prefixed by
-@code{cl-} that were not taken from Common Lisp:
+@code{cl-} that were @emph{not} taken from Common Lisp:
-@c FIXME lexical-let lexical-let*
@example
-cl-callf cl-callf2 cl-defsubst
-cl-floatp-safe cl-letf cl-letf*
+cl-callf cl-callf2 cl-defsubst
+cl-letf cl-letf*
@end example
+@c This is not uninteresting I suppose, but is of zero practical relevance
+@c to the user, and seems like a hostage to changing implementation details.
The following simple functions and macros are defined in @file{cl-lib.el};
they do not cause other components like @file{cl-extra} to be loaded.
@example
-cl-floatp-safe cl-endp
-cl-evenp cl-oddp cl-plusp cl-minusp
-cl-caaar .. cl-cddddr
-cl-list* cl-ldiff cl-rest cl-first .. cl-tenth
-cl-copy-list cl-subst cl-mapcar [2]
-cl-adjoin [3] cl-acons cl-pairlis
-cl-pushnew [3,4] cl-incf [4] cl-decf [4]
-cl-proclaim cl-declaim
+cl-evenp cl-oddp cl-minusp
+cl-plusp cl-endp cl-subst
+cl-copy-list cl-list* cl-ldiff
+cl-rest cl-decf [1] cl-incf [1]
+cl-acons cl-adjoin [2] cl-pairlis
+cl-pushnew [1,2] cl-declaim cl-proclaim
+cl-caaar@dots{}cl-cddddr cl-first@dots{}cl-tenth
+cl-mapcar [3]
@end example
@noindent
-[2] Only for one sequence argument or two list arguments.
+[1] Only when @var{place} is a plain variable name.
@noindent
-[3] Only if @code{:test} is @code{eq}, @code{equal}, or unspecified,
+[2] Only if @code{:test} is @code{eq}, @code{equal}, or unspecified,
and @code{:key} is not used.
@noindent
-[4] Only when @var{place} is a plain variable name.
+[3] Only for one sequence argument or two list arguments.
@node Program Structure
@chapter Program Structure
@noindent
-This section describes features of the @code{CL} package that have to
+This section describes features of this package that have to
do with programs as a whole: advanced argument lists for functions,
and the @code{cl-eval-when} construct.
Instead, this package defines alternates for several Lisp forms
which you must use if you need Common Lisp argument lists.
-@defspec cl-defun name arglist body...
+@defmac cl-defun name arglist body@dots{}
This form is identical to the regular @code{defun} form, except
that @var{arglist} is allowed to be a full Common Lisp argument
list. Also, the function body is enclosed in an implicit block
called @var{name}; @pxref{Blocks and Exits}.
-@end defspec
+@end defmac
-@defspec cl-defsubst name arglist body...
+@defmac cl-defsubst name arglist body@dots{}
This is just like @code{cl-defun}, except that the function that
is defined is automatically proclaimed @code{inline}, i.e.,
calls to it may be expanded into in-line code by the byte compiler.
This is analogous to the @code{defsubst} form;
@code{cl-defsubst} uses a different method (compiler macros) which
works in all versions of Emacs, and also generates somewhat more
+@c For some examples,
+@c see http://lists.gnu.org/archive/html/emacs-devel/2012-11/msg00009.html
efficient inline expansions. In particular, @code{cl-defsubst}
arranges for the processing of keyword arguments, default values,
etc., to be done at compile-time whenever possible.
-@end defspec
+@end defmac
-@defspec cl-defmacro name arglist body...
+@defmac cl-defmacro name arglist body@dots{}
This is identical to the regular @code{defmacro} form,
except that @var{arglist} is allowed to be a full Common Lisp
argument list. The @code{&environment} keyword is supported as
-described in Steele. The @code{&whole} keyword is supported only
+described in Steele's book @cite{Common Lisp, the Language}.
+The @code{&whole} keyword is supported only
within destructured lists (see below); top-level @code{&whole}
cannot be implemented with the current Emacs Lisp interpreter.
The macro expander body is enclosed in an implicit block called
@var{name}.
-@end defspec
+@end defmac
-@defspec cl-function symbol-or-lambda
+@defmac cl-function symbol-or-lambda
This is identical to the regular @code{function} form,
except that if the argument is a @code{lambda} form then that
form may use a full Common Lisp argument list.
-@end defspec
+@end defmac
Also, all forms (such as @code{cl-flet} and @code{cl-labels}) defined
in this package that include @var{arglist}s in their syntax allow
full Common Lisp argument lists.
Note that it is @emph{not} necessary to use @code{cl-defun} in
-order to have access to most @code{CL} features in your function.
+order to have access to most CL features in your function.
These features are always present; @code{cl-defun}'s only
difference from @code{defun} is its more flexible argument
lists and its implicit block.
The full form of a Common Lisp argument list is
@example
-(@var{var}...
- &optional (@var{var} @var{initform} @var{svar})...
+(@var{var}@dots{}
+ &optional (@var{var} @var{initform} @var{svar})@dots{}
&rest @var{var}
- &key ((@var{keyword} @var{var}) @var{initform} @var{svar})...
- &aux (@var{var} @var{initform})...)
+ &key ((@var{keyword} @var{var}) @var{initform} @var{svar})@dots{}
+ &aux (@var{var} @var{initform})@dots{})
@end example
Each of the five argument list sections is optional. The @var{svar},
the ``rest'' argument is bound to the keyword list as it appears
in the call. For example:
-@smallexample
+@example
(cl-defun find-thing (thing &rest rest &key need &allow-other-keys)
(or (apply 'cl-member thing thing-list :allow-other-keys t rest)
(if need (error "Thing not found"))))
-@end smallexample
+@end example
@noindent
This function takes a @code{:need} keyword argument, but also
destructuring is only allowed with @code{defmacro}; this package
allows it with @code{cl-defun} and other argument lists as well.
In destructuring, any argument variable (@var{var} in the above
-diagram) can be replaced by a list of variables, or more generally,
+example) can be replaced by a list of variables, or more generally,
a recursive argument list. The corresponding argument value must
be a list whose elements match this recursive argument list.
For example:
@example
(cl-defmacro dolist ((var listform &optional resultform)
&rest body)
- ...)
+ @dots{})
@end example
This says that the first argument of @code{dolist} must be a list
at compile-time so that later parts of the file can refer to the
macros that are defined.
-@defspec cl-eval-when (situations...) forms...
+@defmac cl-eval-when (situations@dots{}) forms@dots{}
This form controls when the body @var{forms} are evaluated.
The @var{situations} list may contain any set of the symbols
@code{compile}, @code{load}, and @code{eval} (or their long-winded
certain top-level forms, like @code{defmacro} (sort-of) and
@code{require}, as if they were wrapped in @code{(cl-eval-when
(compile load eval) @dots{})}.
-@end defspec
+@end defmac
Emacs includes two special forms related to @code{cl-eval-when}.
+@xref{Eval During Compile,,,elisp,GNU Emacs Lisp Reference Manual}.
One of these, @code{eval-when-compile}, is not quite equivalent to
any @code{cl-eval-when} construct and is described below.
The other form, @code{(eval-and-compile @dots{})}, is exactly
-equivalent to @samp{(cl-eval-when (compile load eval) @dots{})} and
-so is not itself defined by this package.
+equivalent to @samp{(cl-eval-when (compile load eval) @dots{})}.
-@defspec eval-when-compile forms...
+@defmac eval-when-compile forms@dots{}
The @var{forms} are evaluated at compile-time; at execution time,
this form acts like a quoted constant of the resulting value. Used
at top-level, @code{eval-when-compile} is just like @samp{eval-when
or other reasons.
This form is similar to the @samp{#.} syntax of true Common Lisp.
-@end defspec
+@end defmac
-@defspec cl-load-time-value form
+@defmac cl-load-time-value form
The @var{form} is evaluated at load-time; at execution time,
this form acts like a quoted constant of the resulting value.
(insert "This function was executed on: "
(current-time-string)
", compiled on: "
- '"Wed Jun 23 18:33:43 1993"
+ '"Wed Oct 31 16:32:28 2012"
", and loaded on: "
--temp--))
@end example
-@end defspec
+@end defmac
@node Predicates
@chapter Predicates
The type symbols @code{character} and @code{string-char} match
integers in the range from 0 to 255.
+@c No longer relevant, so covered by first item above (float -> floatp).
+@ignore
@item
The type symbol @code{float} uses the @code{cl-floatp-safe} predicate
defined by this package rather than @code{floatp}, so it will work
correctly even in Emacs versions without floating-point support.
+@end ignore
@item
The type list @code{(integer @var{low} @var{high})} represents all
error.
@end defun
-@defspec cl-deftype name arglist forms...
+@defmac cl-deftype name arglist forms@dots{}
This macro defines a new type called @var{name}. It is similar
to @code{defmacro} in many ways; when @var{name} is encountered
as a type name, the body @var{forms} are evaluated and should
return a type specifier that is equivalent to the type. The
@var{arglist} is a Common Lisp argument list of the sort accepted
-by @code{cl-defmacro}. The type specifier @samp{(@var{name} @var{args}...)}
+by @code{cl-defmacro}. The type specifier @samp{(@var{name} @var{args}@dots{})}
is expanded by calling the expander with those arguments; the type
symbol @samp{@var{name}} is expanded by calling the expander with
no arguments. The @var{arglist} is processed the same as for
The last example shows how the Common Lisp @code{unsigned-byte}
type specifier could be implemented if desired; this package does
not implement @code{unsigned-byte} by default.
-@end defspec
+@end defmac
-The @code{cl-typecase} and @code{cl-check-type} macros also use type
-names. @xref{Conditionals}. @xref{Assertions}. The @code{cl-map},
+The @code{cl-typecase} (@pxref{Conditionals}) and @code{cl-check-type}
+(@pxref{Assertions}) macros also use type names. The @code{cl-map},
@code{cl-concatenate}, and @code{cl-merge} functions take type-name
arguments to specify the type of sequence to return. @xref{Sequences}.
standard @code{setf} facility, and a number of looping and conditional
constructs.
-@c FIXME
-@c lexical-let is obsolete; flet is not cl-flet.
-@c values is not cl-values.
@menu
* Assignment:: The @code{cl-psetq} form.
* Generalized Variables:: Extensions to generalized variables.
-* Variable Bindings:: @code{cl-progv}, @code{lexical-let}, @code{flet}, @code{cl-macrolet}.
+* Variable Bindings:: @code{cl-progv}, @code{cl-flet}, @code{cl-macrolet}.
* Conditionals:: @code{cl-case}, @code{cl-typecase}.
* Blocks and Exits:: @code{cl-block}, @code{cl-return}, @code{cl-return-from}.
* Iteration:: @code{cl-do}, @code{cl-dotimes}, @code{cl-dolist}, @code{cl-do-symbols}.
-* Loop Facility:: The Common Lisp @code{cl-loop} macro.
-* Multiple Values:: @code{values}, @code{cl-multiple-value-bind}, etc.
+* Loop Facility:: The Common Lisp @code{loop} macro.
+* Multiple Values:: @code{cl-values}, @code{cl-multiple-value-bind}, etc.
@end menu
@node Assignment
The @code{cl-psetq} form is just like @code{setq}, except that multiple
assignments are done in parallel rather than sequentially.
-@defspec cl-psetq [symbol form]@dots{}
+@defmac cl-psetq [symbol form]@dots{}
This special form (actually a macro) is used to assign to several
variables simultaneously. Given only one @var{symbol} and @var{form},
it has the same effect as @code{setq}. Given several @var{symbol}
@pxref{Modify Macros}.)
@code{cl-psetq} always returns @code{nil}.
-@end defspec
+@end defmac
@node Generalized Variables
@section Generalized Variables
A @dfn{generalized variable} or @dfn{place form} is one of the many
places in Lisp memory where values can be stored. The simplest place
-form is a regular Lisp variable. But the cars and cdrs of lists,
+form is a regular Lisp variable. But the @sc{car}s and @sc{cdr}s of lists,
elements of arrays, properties of symbols, and many other locations
are also places where Lisp values are stored. For basic information,
@pxref{Generalized Variables,,,elisp,GNU Emacs Lisp Reference Manual}.
@menu
* Setf Extensions:: Additional @code{setf} places.
-* Modify Macros:: @code{cl-incf}, @code{cl-rotatef}, @code{letf}, @code{cl-callf}, etc.
-* Customizing Setf:: @code{define-modify-macro}, @code{defsetf}, @code{define-setf-method}.
+* Modify Macros:: @code{cl-incf}, @code{cl-rotatef}, @code{cl-letf}, @code{cl-callf}, etc.
@end menu
@node Setf Extensions
@subsection Setf Extensions
-Several standard (e.g. @code{car}) and Emacs-specific
-(e.g. @code{window-point}) Lisp functions are @code{setf}-able by default.
+Several standard (e.g., @code{car}) and Emacs-specific
+(e.g., @code{window-point}) Lisp functions are @code{setf}-able by default.
This package defines @code{setf} handlers for several additional functions:
@itemize
@item
-Functions from @code{CL} itself:
-@smallexample
-cl-caaar .. cl-cddddr cl-first .. cl-tenth
-cl-rest cl-get cl-getf cl-subseq
-@end smallexample
+Functions from this package:
+@example
+cl-rest cl-subseq cl-get cl-getf
+cl-caaar@dots{}cl-cddddr cl-first@dots{}cl-tenth
+@end example
+
+@noindent
+Note that for @code{cl-getf} (as for @code{nthcdr}), the list argument
+of the function must itself be a valid @var{place} form.
@item
General Emacs Lisp functions:
-@smallexample
+@example
buffer-file-name getenv
buffer-modified-p global-key-binding
buffer-name local-key-binding
frame-visible-p x-get-secondary-selection
frame-width x-get-selection
get-register
-@end smallexample
+@end example
Most of these have directly corresponding ``set'' functions, like
@code{use-local-map} for @code{current-local-map}, or @code{goto-char}
The generalized variable @code{buffer-substring}, listed above,
also works in this way by replacing a portion of the current buffer.
-@c FIXME? Also `eq'? (see cl-lib.el)
+@c FIXME? Also `eq'? (see cl-lib.el)
+@c Currently commented out in cl.el.
+@ignore
@item
A call of the form @code{(apply '@var{func} @dots{})} or
@code{(apply (function @var{func}) @dots{})}, where @var{func}
Emacs place functions are suitable in this sense, this feature is
only interesting when used with places you define yourself with
@code{define-setf-method} or the long form of @code{defsetf}.
+@xref{Obsolete Setf Customization}.
+@end ignore
+@c FIXME? Is this still true?
@item
A macro call, in which case the macro is expanded and @code{setf}
is applied to the resulting form.
-
-@item
-Any form for which a @code{defsetf} or @code{define-setf-method}
-has been made.
@end itemize
@c FIXME should this be in lispref? It seems self-evident.
@c Contrast with the cl-incf example later on.
-@c Here it really only serves as a constrast to wrong-order.
+@c Here it really only serves as a contrast to wrong-order.
The @code{setf} macro takes care to evaluate all subforms in
the proper left-to-right order; for example,
variables. Many are interesting and useful even when the @var{place}
is just a variable name.
-@defspec cl-psetf [place form]@dots{}
+@defmac cl-psetf [place form]@dots{}
This macro is to @code{setf} what @code{cl-psetq} is to @code{setq}:
When several @var{place}s and @var{form}s are involved, the
assignments take place in parallel rather than sequentially.
Specifically, all subforms are evaluated from left to right, then
all the assignments are done (in an undefined order).
-@end defspec
+@end defmac
-@defspec cl-incf place &optional x
+@defmac cl-incf place &optional x
This macro increments the number stored in @var{place} by one, or
by @var{x} if specified. The incremented value is returned. For
example, @code{(cl-incf i)} is equivalent to @code{(setq i (1+ i))}, and
As a more Emacs-specific example of @code{cl-incf}, the expression
@code{(cl-incf (point) @var{n})} is essentially equivalent to
@code{(forward-char @var{n})}.
-@end defspec
+@end defmac
-@defspec cl-decf place &optional x
+@defmac cl-decf place &optional x
This macro decrements the number stored in @var{place} by one, or
by @var{x} if specified.
-@end defspec
+@end defmac
-@defspec cl-pushnew x place @t{&key :test :test-not :key}
+@defmac cl-pushnew x place @t{&key :test :test-not :key}
This macro inserts @var{x} at the front of the list stored in
@var{place}, but only if @var{x} was not @code{eql} to any
existing element of the list. The optional keyword arguments
are interpreted in the same way as for @code{cl-adjoin}.
@xref{Lists as Sets}.
-@end defspec
+@end defmac
-@defspec cl-shiftf place@dots{} newvalue
+@defmac cl-shiftf place@dots{} newvalue
This macro shifts the @var{place}s left by one, shifting in the
value of @var{newvalue} (which may be any Lisp expression, not just
a generalized variable), and returning the value shifted out of
@noindent
except that the subforms of @var{a}, @var{b}, and @var{c} are actually
evaluated only once each and in the apparent order.
-@end defspec
+@end defmac
-@defspec cl-rotatef place@dots{}
+@defmac cl-rotatef place@dots{}
This macro rotates the @var{place}s left by one in circular fashion.
Thus, @code{(cl-rotatef @var{a} @var{b} @var{c} @var{d})} is equivalent to
except for the evaluation of subforms. @code{cl-rotatef} always
returns @code{nil}. Note that @code{(cl-rotatef @var{a} @var{b})}
conveniently exchanges @var{a} and @var{b}.
-@end defspec
+@end defmac
The following macros were invented for this package; they have no
analogues in Common Lisp.
-@defspec letf (bindings@dots{}) forms@dots{}
+@defmac cl-letf (bindings@dots{}) forms@dots{}
This macro is analogous to @code{let}, but for generalized variables
rather than just symbols. Each @var{binding} should be of the form
@code{(@var{place} @var{value})}; the original contents of the
For example,
@example
-(letf (((point) (point-min))
- (a 17))
- ...)
+(cl-letf (((point) (point-min))
+ (a 17))
+ @dots{})
@end example
@noindent
-moves ``point'' in the current buffer to the beginning of the buffer,
+moves point in the current buffer to the beginning of the buffer,
and also binds @code{a} to 17 (as if by a normal @code{let}, since
@code{a} is just a regular variable). After the body exits, @code{a}
is set back to its original value and point is moved back to its
original position.
-Note that @code{letf} on @code{(point)} is not quite like a
+Note that @code{cl-letf} on @code{(point)} is not quite like a
@code{save-excursion}, as the latter effectively saves a marker
which tracks insertions and deletions in the buffer. Actually,
-a @code{letf} of @code{(point-marker)} is much closer to this
+a @code{cl-letf} of @code{(point-marker)} is much closer to this
behavior. (@code{point} and @code{point-marker} are equivalent
as @code{setf} places; each will accept either an integer or a
marker as the stored value.)
Since generalized variables look like lists, @code{let}'s shorthand
of using @samp{foo} for @samp{(foo nil)} as a @var{binding} would
-be ambiguous in @code{letf} and is not allowed.
+be ambiguous in @code{cl-letf} and is not allowed.
However, a @var{binding} specifier may be a one-element list
@samp{(@var{place})}, which is similar to @samp{(@var{place}
@var{place})}. In other words, the @var{place} is not disturbed
-on entry to the body, and the only effect of the @code{letf} is
-to restore the original value of @var{place} afterwards. (The
-redundant access-and-store suggested by the @code{(@var{place}
+on entry to the body, and the only effect of the @code{cl-letf} is
+to restore the original value of @var{place} afterwards.
+@c I suspect this may no longer be true; either way it's
+@c implementation detail and so not essential to document.
+@ignore
+(The redundant access-and-store suggested by the @code{(@var{place}
@var{place})} example does not actually occur.)
+@end ignore
+
+Note that in this case, and in fact almost every case, @var{place}
+must have a well-defined value outside the @code{cl-letf} body.
+There is essentially only one exception to this, which is @var{place}
+a plain variable with a specified @var{value} (such as @code{(a 17)}
+in the above example).
+@c See http://debbugs.gnu.org/12758
+@c Some or all of this was true for cl.el, but not for cl-lib.el.
+@ignore
+The only exceptions are plain variables and calls to
+@code{symbol-value} and @code{symbol-function}. If the symbol is not
+bound on entry, it is simply made unbound by @code{makunbound} or
+@code{fmakunbound} on exit.
+@end ignore
-In most cases, the @var{place} must have a well-defined value on
-entry to the @code{letf} form. The only exceptions are plain
-variables and calls to @code{symbol-value} and @code{symbol-function}.
-If the symbol is not bound on entry, it is simply made unbound by
-@code{makunbound} or @code{fmakunbound} on exit.
-@end defspec
+Note that the @file{cl.el} version of this macro behaves slightly
+differently. @xref{Obsolete Macros}.
+@end defmac
-@defspec cl-letf* (bindings@dots{}) forms@dots{}
-This macro is to @code{letf} what @code{let*} is to @code{let}:
+@defmac cl-letf* (bindings@dots{}) forms@dots{}
+This macro is to @code{cl-letf} what @code{let*} is to @code{let}:
It does the bindings in sequential rather than parallel order.
-@end defspec
+@end defmac
-@defspec cl-callf @var{function} @var{place} @var{args}@dots{}
+@defmac cl-callf @var{function} @var{place} @var{args}@dots{}
This is the ``generic'' modify macro. It calls @var{function},
which should be an unquoted function name, macro name, or lambda.
It passes @var{place} and @var{args} as arguments, and assigns the
(cl-callf cl-union happy-people (list joe bob) :test 'same-person)
@end example
-@xref{Customizing Setf}, for @code{define-modify-macro}, a way
-to create even more concise notations for modify macros. Note
-again that @code{cl-callf} is an extension to standard Common Lisp.
-@end defspec
+Note again that @code{cl-callf} is an extension to standard Common Lisp.
+@end defmac
-@defspec cl-callf2 @var{function} @var{arg1} @var{place} @var{args}@dots{}
+@defmac cl-callf2 @var{function} @var{arg1} @var{place} @var{args}@dots{}
This macro is like @code{cl-callf}, except that @var{place} is
the @emph{second} argument of @var{function} rather than the
first. For example, @code{(push @var{x} @var{place})} is
equivalent to @code{(cl-callf2 cons @var{x} @var{place})}.
-@end defspec
+@end defmac
The @code{cl-callf} and @code{cl-callf2} macros serve as building
-blocks for other macros like @code{cl-incf}, @code{cl-pushnew}, and
-@code{define-modify-macro}. The @code{letf} and @code{cl-letf*}
-macros are used in the processing of symbol macros;
-@pxref{Macro Bindings}.
+blocks for other macros like @code{cl-incf}, and @code{cl-pushnew}.
+The @code{cl-letf} and @code{cl-letf*} macros are used in the processing
+of symbol macros; @pxref{Macro Bindings}.
-@node Customizing Setf
-@subsection Customizing Setf
+
+@node Variable Bindings
+@section Variable Bindings
@noindent
-Common Lisp defines three macros, @code{define-modify-macro},
-@code{defsetf}, and @code{define-setf-method}, that allow the
-user to extend generalized variables in various ways.
+These Lisp forms make bindings to variables and function names,
+analogous to Lisp's built-in @code{let} form.
-@defspec define-modify-macro name arglist function [doc-string]
-This macro defines a ``read-modify-write'' macro similar to
-@code{cl-incf} and @code{cl-decf}. The macro @var{name} is defined
-to take a @var{place} argument followed by additional arguments
-described by @var{arglist}. The call
+@xref{Modify Macros}, for the @code{cl-letf} and @code{cl-letf*} forms which
+are also related to variable bindings.
-@example
-(@var{name} @var{place} @var{args}...)
-@end example
+@menu
+* Dynamic Bindings:: The @code{cl-progv} form.
+* Function Bindings:: @code{cl-flet} and @code{cl-labels}.
+* Macro Bindings:: @code{cl-macrolet} and @code{cl-symbol-macrolet}.
+@end menu
+
+@node Dynamic Bindings
+@subsection Dynamic Bindings
@noindent
-will be expanded to
+The standard @code{let} form binds variables whose names are known
+at compile-time. The @code{cl-progv} form provides an easy way to
+bind variables whose names are computed at run-time.
-@example
-(cl-callf @var{func} @var{place} @var{args}...)
-@end example
+@defmac cl-progv symbols values forms@dots{}
+This form establishes @code{let}-style variable bindings on a
+set of variables computed at run-time. The expressions
+@var{symbols} and @var{values} are evaluated, and must return lists
+of symbols and values, respectively. The symbols are bound to the
+corresponding values for the duration of the body @var{form}s.
+If @var{values} is shorter than @var{symbols}, the last few symbols
+are bound to @code{nil}.
+If @var{symbols} is shorter than @var{values}, the excess values
+are ignored.
+@end defmac
+
+@node Function Bindings
+@subsection Function Bindings
@noindent
-which in turn is roughly equivalent to
+These forms make @code{let}-like bindings to functions instead
+of variables.
-@example
-(setf @var{place} (@var{func} @var{place} @var{args}...))
-@end example
+@defmac cl-flet (bindings@dots{}) forms@dots{}
+This form establishes @code{let}-style bindings on the function
+cells of symbols rather than on the value cells. Each @var{binding}
+must be a list of the form @samp{(@var{name} @var{arglist}
+@var{forms}@dots{})}, which defines a function exactly as if
+it were a @code{cl-defun} form. The function @var{name} is defined
+accordingly for the duration of the body of the @code{cl-flet}; then
+the old function definition, or lack thereof, is restored.
-For example:
+You can use @code{cl-flet} to disable or modify the behavior of
+functions (including Emacs primitives) in a temporary, localized fashion.
+(Compare this with the idea of advising functions.
+@xref{Advising Functions,,,elisp,GNU Emacs Lisp Reference Manual}.)
+
+The bindings are lexical in scope. This means that all references to
+the named functions must appear physically within the body of the
+@code{cl-flet} form.
+
+Functions defined by @code{cl-flet} may use the full Common Lisp
+argument notation supported by @code{cl-defun}; also, the function
+body is enclosed in an implicit block as if by @code{cl-defun}.
+@xref{Program Structure}.
+
+Note that the @file{cl.el} version of this macro behaves slightly
+differently. In particular, its binding is dynamic rather than
+lexical. @xref{Obsolete Macros}.
+@end defmac
+
+@defmac cl-labels (bindings@dots{}) forms@dots{}
+The @code{cl-labels} form is like @code{cl-flet}, except that
+the function bindings can be recursive. The scoping is lexical,
+but you can only capture functions in closures if
+@code{lexical-binding} is @code{t}.
+@xref{Closures,,,elisp,GNU Emacs Lisp Reference Manual}, and
+@ref{Using Lexical Binding,,,elisp,GNU Emacs Lisp Reference Manual}.
+
+Lexical scoping means that all references to the named
+functions must appear physically within the body of the
+@code{cl-labels} form. References may appear both in the body
+@var{forms} of @code{cl-labels} itself, and in the bodies of
+the functions themselves. Thus, @code{cl-labels} can define
+local recursive functions, or mutually-recursive sets of functions.
+
+A ``reference'' to a function name is either a call to that
+function, or a use of its name quoted by @code{quote} or
+@code{function} to be passed on to, say, @code{mapcar}.
+
+Note that the @file{cl.el} version of this macro behaves slightly
+differently. @xref{Obsolete Macros}.
+@end defmac
+
+@node Macro Bindings
+@subsection Macro Bindings
+
+@noindent
+These forms create local macros and ``symbol macros''.
+
+@defmac cl-macrolet (bindings@dots{}) forms@dots{}
+This form is analogous to @code{cl-flet}, but for macros instead of
+functions. Each @var{binding} is a list of the same form as the
+arguments to @code{cl-defmacro} (i.e., a macro name, argument list,
+and macro-expander forms). The macro is defined accordingly for
+use within the body of the @code{cl-macrolet}.
+
+Because of the nature of macros, @code{cl-macrolet} is always lexically
+scoped. The @code{cl-macrolet} binding will
+affect only calls that appear physically within the body
+@var{forms}, possibly after expansion of other macros in the
+body.
+@end defmac
+
+@defmac cl-symbol-macrolet (bindings@dots{}) forms@dots{}
+This form creates @dfn{symbol macros}, which are macros that look
+like variable references rather than function calls. Each
+@var{binding} is a list @samp{(@var{var} @var{expansion})};
+any reference to @var{var} within the body @var{forms} is
+replaced by @var{expansion}.
@example
-(define-modify-macro cl-incf (&optional (n 1)) +)
-(define-modify-macro cl-concatf (&rest args) concat)
+(setq bar '(5 . 9))
+(cl-symbol-macrolet ((foo (car bar)))
+ (cl-incf foo))
+bar
+ @result{} (6 . 9)
@end example
-Note that @code{&key} is not allowed in @var{arglist}, but
-@code{&rest} is sufficient to pass keywords on to the function.
+A @code{setq} of a symbol macro is treated the same as a @code{setf}.
+I.e., @code{(setq foo 4)} in the above would be equivalent to
+@code{(setf foo 4)}, which in turn expands to @code{(setf (car bar) 4)}.
-Most of the modify macros defined by Common Lisp do not exactly
-follow the pattern of @code{define-modify-macro}. For example,
-@code{push} takes its arguments in the wrong order, and @code{pop}
-is completely irregular. You can define these macros ``by hand''
-using @code{get-setf-method}, or consult the source
-to see how to use the internal @code{setf} building blocks.
-@end defspec
+Likewise, a @code{let} or @code{let*} binding a symbol macro is
+treated like a @code{cl-letf} or @code{cl-letf*}. This differs from true
+Common Lisp, where the rules of lexical scoping cause a @code{let}
+binding to shadow a @code{symbol-macrolet} binding. In this package,
+such shadowing does not occur, even when @code{lexical-binding} is
+@c See http://debbugs.gnu.org/12119
+@code{t}. (This behavior predates the addition of lexical binding to
+Emacs Lisp, and may change in future to respect @code{lexical-binding}.)
+At present in this package, only @code{lexical-let} and
+@code{lexical-let*} will shadow a symbol macro. @xref{Obsolete
+Lexical Binding}.
-@defspec defsetf access-fn update-fn
-This is the simpler of two @code{defsetf} forms. Where
-@var{access-fn} is the name of a function which accesses a place,
-this declares @var{update-fn} to be the corresponding store
-function. From now on,
+There is no analogue of @code{defmacro} for symbol macros; all symbol
+macros are local. A typical use of @code{cl-symbol-macrolet} is in the
+expansion of another macro:
@example
-(setf (@var{access-fn} @var{arg1} @var{arg2} @var{arg3}) @var{value})
+(cl-defmacro my-dolist ((x list) &rest body)
+ (let ((var (cl-gensym)))
+ (list 'cl-loop 'for var 'on list 'do
+ (cl-list* 'cl-symbol-macrolet
+ (list (list x (list 'car var)))
+ body))))
+
+(setq mylist '(1 2 3 4))
+(my-dolist (x mylist) (cl-incf x))
+mylist
+ @result{} (2 3 4 5)
@end example
@noindent
-will be expanded to
+In this example, the @code{my-dolist} macro is similar to @code{dolist}
+(@pxref{Iteration}) except that the variable @code{x} becomes a true
+reference onto the elements of the list. The @code{my-dolist} call
+shown here expands to
@example
-(@var{update-fn} @var{arg1} @var{arg2} @var{arg3} @var{value})
+(cl-loop for G1234 on mylist do
+ (cl-symbol-macrolet ((x (car G1234)))
+ (cl-incf x)))
@end example
@noindent
-The @var{update-fn} is required to be either a true function, or
-a macro which evaluates its arguments in a function-like way. Also,
-the @var{update-fn} is expected to return @var{value} as its result.
-Otherwise, the above expansion would not obey the rules for the way
-@code{setf} is supposed to behave.
-
-As a special (non-Common-Lisp) extension, a third argument of @code{t}
-to @code{defsetf} says that the @code{update-fn}'s return value is
-not suitable, so that the above @code{setf} should be expanded to
-something more like
+which in turn expands to
@example
-(let ((temp @var{value}))
- (@var{update-fn} @var{arg1} @var{arg2} @var{arg3} temp)
- temp)
+(cl-loop for G1234 on mylist do (cl-incf (car G1234)))
@end example
-Some examples of the use of @code{defsetf}, drawn from the standard
-suite of setf methods, are:
+@xref{Loop Facility}, for a description of the @code{cl-loop} macro.
+This package defines a nonstandard @code{in-ref} loop clause that
+works much like @code{my-dolist}.
+@end defmac
+
+@node Conditionals
+@section Conditionals
-@example
-(defsetf car setcar)
-(defsetf symbol-value set)
-(defsetf buffer-name rename-buffer t)
-@end example
-@end defspec
-
-@defspec defsetf access-fn arglist (store-var) forms@dots{}
-This is the second, more complex, form of @code{defsetf}. It is
-rather like @code{defmacro} except for the additional @var{store-var}
-argument. The @var{forms} should return a Lisp form which stores
-the value of @var{store-var} into the generalized variable formed
-by a call to @var{access-fn} with arguments described by @var{arglist}.
-The @var{forms} may begin with a string which documents the @code{setf}
-method (analogous to the doc string that appears at the front of a
-function).
+@noindent
+These conditional forms augment Emacs Lisp's simple @code{if},
+@code{and}, @code{or}, and @code{cond} forms.
-For example, the simple form of @code{defsetf} is shorthand for
+@defmac cl-case keyform clause@dots{}
+This macro evaluates @var{keyform}, then compares it with the key
+values listed in the various @var{clause}s. Whichever clause matches
+the key is executed; comparison is done by @code{eql}. If no clause
+matches, the @code{cl-case} form returns @code{nil}. The clauses are
+of the form
@example
-(defsetf @var{access-fn} (&rest args) (store)
- (append '(@var{update-fn}) args (list store)))
+(@var{keylist} @var{body-forms}@dots{})
@end example
-The Lisp form that is returned can access the arguments from
-@var{arglist} and @var{store-var} in an unrestricted fashion;
-macros like @code{setf} and @code{cl-incf} which invoke this
-setf-method will insert temporary variables as needed to make
-sure the apparent order of evaluation is preserved.
+@noindent
+where @var{keylist} is a list of key values. If there is exactly
+one value, and it is not a cons cell or the symbol @code{nil} or
+@code{t}, then it can be used by itself as a @var{keylist} without
+being enclosed in a list. All key values in the @code{cl-case} form
+must be distinct. The final clauses may use @code{t} in place of
+a @var{keylist} to indicate a default clause that should be taken
+if none of the other clauses match. (The symbol @code{otherwise}
+is also recognized in place of @code{t}. To make a clause that
+matches the actual symbol @code{t}, @code{nil}, or @code{otherwise},
+enclose the symbol in a list.)
-Another example drawn from the standard package:
+For example, this expression reads a keystroke, then does one of
+four things depending on whether it is an @samp{a}, a @samp{b},
+a @key{RET} or @kbd{C-j}, or anything else.
@example
-(defsetf nth (n x) (store)
- (list 'setcar (list 'nthcdr n x) store))
+(cl-case (read-char)
+ (?a (do-a-thing))
+ (?b (do-b-thing))
+ ((?\r ?\n) (do-ret-thing))
+ (t (do-other-thing)))
@end example
-@end defspec
+@end defmac
-@defspec define-setf-method access-fn arglist forms@dots{}
-This is the most general way to create new place forms. When
-a @code{setf} to @var{access-fn} with arguments described by
-@var{arglist} is expanded, the @var{forms} are evaluated and
-must return a list of five items:
+@defmac cl-ecase keyform clause@dots{}
+This macro is just like @code{cl-case}, except that if the key does
+not match any of the clauses, an error is signaled rather than
+simply returning @code{nil}.
+@end defmac
-@enumerate
-@item
-A list of @dfn{temporary variables}.
+@defmac cl-typecase keyform clause@dots{}
+This macro is a version of @code{cl-case} that checks for types
+rather than values. Each @var{clause} is of the form
+@samp{(@var{type} @var{body}@dots{})}. @xref{Type Predicates},
+for a description of type specifiers. For example,
-@item
-A list of @dfn{value forms} corresponding to the temporary variables
-above. The temporary variables will be bound to these value forms
-as the first step of any operation on the generalized variable.
+@example
+(cl-typecase x
+ (integer (munch-integer x))
+ (float (munch-float x))
+ (string (munch-integer (string-to-int x)))
+ (t (munch-anything x)))
+@end example
-@item
-A list of exactly one @dfn{store variable} (generally obtained
-from a call to @code{gensym}).
+The type specifier @code{t} matches any type of object; the word
+@code{otherwise} is also allowed. To make one clause match any of
+several types, use an @code{(or @dots{})} type specifier.
+@end defmac
-@item
-A Lisp form which stores the contents of the store variable into
-the generalized variable, assuming the temporaries have been
-bound as described above.
+@defmac cl-etypecase keyform clause@dots{}
+This macro is just like @code{cl-typecase}, except that if the key does
+not match any of the clauses, an error is signaled rather than
+simply returning @code{nil}.
+@end defmac
-@item
-A Lisp form which accesses the contents of the generalized variable,
-assuming the temporaries have been bound.
-@end enumerate
+@node Blocks and Exits
+@section Blocks and Exits
-This is exactly like the Common Lisp macro of the same name,
-except that the method returns a list of five values rather
-than the five values themselves, since Emacs Lisp does not
-support Common Lisp's notion of multiple return values.
+@noindent
+Common Lisp @dfn{blocks} provide a non-local exit mechanism very
+similar to @code{catch} and @code{throw}, with lexical scoping.
+This package actually implements @code{cl-block}
+in terms of @code{catch}; however, the lexical scoping allows the
+byte-compiler to omit the costly @code{catch} step if the
+body of the block does not actually @code{cl-return-from} the block.
-Once again, the @var{forms} may begin with a documentation string.
+@defmac cl-block name forms@dots{}
+The @var{forms} are evaluated as if by a @code{progn}. However,
+if any of the @var{forms} execute @code{(cl-return-from @var{name})},
+they will jump out and return directly from the @code{cl-block} form.
+The @code{cl-block} returns the result of the last @var{form} unless
+a @code{cl-return-from} occurs.
-A setf-method should be maximally conservative with regard to
-temporary variables. In the setf-methods generated by
-@code{defsetf}, the second return value is simply the list of
-arguments in the place form, and the first return value is a
-list of a corresponding number of temporary variables generated
-by @code{cl-gensym}. Macros like @code{setf} and @code{cl-incf} which
-use this setf-method will optimize away most temporaries that
-turn out to be unnecessary, so there is little reason for the
-setf-method itself to optimize.
-@end defspec
+The @code{cl-block}/@code{cl-return-from} mechanism is quite similar to
+the @code{catch}/@code{throw} mechanism. The main differences are
+that block @var{name}s are unevaluated symbols, rather than forms
+(such as quoted symbols) that evaluate to a tag at run-time; and
+also that blocks are always lexically scoped.
+In a dynamically scoped @code{catch}, functions called from the
+@code{catch} body can also @code{throw} to the @code{catch}. This
+is not an option for @code{cl-block}, where
+the @code{cl-return-from} referring to a block name must appear
+physically within the @var{forms} that make up the body of the block.
+They may not appear within other called functions, although they may
+appear within macro expansions or @code{lambda}s in the body. Block
+names and @code{catch} names form independent name-spaces.
-@defun get-setf-method place &optional env
-This function returns the setf-method for @var{place}, by
-invoking the definition previously recorded by @code{defsetf}
-or @code{define-setf-method}. The result is a list of five
-values as described above. You can use this function to build
-your own @code{cl-incf}-like modify macros. (Actually, it is
-@c FIXME?
-better to use the internal functions @code{cl-setf-do-modify}
-and @code{cl-setf-do-store}, which are a bit easier to use and
-which also do a number of optimizations; consult the source
-code for the @code{cl-incf} function for a simple example.)
+In true Common Lisp, @code{defun} and @code{defmacro} surround
+the function or expander bodies with implicit blocks with the
+same name as the function or macro. This does not occur in Emacs
+Lisp, but this package provides @code{cl-defun} and @code{cl-defmacro}
+forms, which do create the implicit block.
-The argument @var{env} specifies the ``environment'' to be
-passed on to @code{macroexpand} if @code{get-setf-method} should
-need to expand a macro in @var{place}. It should come from
-an @code{&environment} argument to the macro or setf-method
-that called @code{get-setf-method}.
+The Common Lisp looping constructs defined by this package,
+such as @code{cl-loop} and @code{cl-dolist}, also create implicit blocks
+just as in Common Lisp.
-See also the source code for the setf-methods for @code{apply}
-and @code{substring}, each of which works by calling
-@code{get-setf-method} on a simpler case, then massaging
-the result in various ways.
-@end defun
+Because they are implemented in terms of Emacs Lisp's @code{catch}
+and @code{throw}, blocks have the same overhead as actual
+@code{catch} constructs (roughly two function calls). However,
+the byte compiler will optimize away the @code{catch}
+if the block does
+not in fact contain any @code{cl-return} or @code{cl-return-from} calls
+that jump to it. This means that @code{cl-do} loops and @code{cl-defun}
+functions that don't use @code{cl-return} don't pay the overhead to
+support it.
+@end defmac
+
+@defmac cl-return-from name [result]
+This macro returns from the block named @var{name}, which must be
+an (unevaluated) symbol. If a @var{result} form is specified, it
+is evaluated to produce the result returned from the @code{block}.
+Otherwise, @code{nil} is returned.
+@end defmac
-Modern Common Lisp defines a second, independent way to specify
-the @code{setf} behavior of a function, namely ``@code{setf}
-functions'' whose names are lists @code{(setf @var{name})}
-rather than symbols. For example, @code{(defun (setf foo) @dots{})}
-defines the function that is used when @code{setf} is applied to
-@code{foo}. This package does not currently support @code{setf}
-functions. In particular, it is a compile-time error to use
-@code{setf} on a form which has not already been @code{defsetf}'d
-or otherwise declared; in newer Common Lisps, this would not be
-an error since the function @code{(setf @var{func})} might be
-defined later.
+@defmac cl-return [result]
+This macro is exactly like @code{(cl-return-from nil @var{result})}.
+Common Lisp loops like @code{cl-do} and @code{cl-dolist} implicitly enclose
+themselves in @code{nil} blocks.
+@end defmac
-@node Variable Bindings
-@section Variable Bindings
+@node Iteration
+@section Iteration
@noindent
-These Lisp forms make bindings to variables and function names,
-analogous to Lisp's built-in @code{let} form.
+The macros described here provide more sophisticated, high-level
+looping constructs to complement Emacs Lisp's basic loop forms
+(@pxref{Iteration,,,elisp,GNU Emacs Lisp Reference Manual}).
-@xref{Modify Macros}, for the @code{letf} and @code{cl-letf*} forms which
-are also related to variable bindings.
+@defmac cl-loop forms@dots{}
+This package supports both the simple, old-style meaning of
+@code{loop} and the extremely powerful and flexible feature known as
+the @dfn{Loop Facility} or @dfn{Loop Macro}. This more advanced
+facility is discussed in the following section; @pxref{Loop Facility}.
+The simple form of @code{loop} is described here.
-@menu
-* Dynamic Bindings:: The @code{cl-progv} form.
-* Lexical Bindings:: @code{lexical-let} and lexical closures.
-* Function Bindings:: @code{flet} and @code{labels}.
-* Macro Bindings:: @code{cl-macrolet} and @code{cl-symbol-macrolet}.
-@end menu
+If @code{cl-loop} is followed by zero or more Lisp expressions,
+then @code{(cl-loop @var{exprs}@dots{})} simply creates an infinite
+loop executing the expressions over and over. The loop is
+enclosed in an implicit @code{nil} block. Thus,
-@node Dynamic Bindings
-@subsection Dynamic Bindings
+@example
+(cl-loop (foo) (if (no-more) (return 72)) (bar))
+@end example
@noindent
-The standard @code{let} form binds variables whose names are known
-at compile-time. The @code{cl-progv} form provides an easy way to
-bind variables whose names are computed at run-time.
-
-@defspec cl-progv symbols values forms@dots{}
-This form establishes @code{let}-style variable bindings on a
-set of variables computed at run-time. The expressions
-@var{symbols} and @var{values} are evaluated, and must return lists
-of symbols and values, respectively. The symbols are bound to the
-corresponding values for the duration of the body @var{form}s.
-If @var{values} is shorter than @var{symbols}, the last few symbols
-are bound to @code{nil}.
-If @var{symbols} is shorter than @var{values}, the excess values
-are ignored.
-@end defspec
+is exactly equivalent to
-@node Lexical Bindings
-@subsection Lexical Bindings
+@example
+(cl-block nil (while t (foo) (if (no-more) (return 72)) (bar)))
+@end example
-@noindent
-The @code{CL} package defines the following macro which
-more closely follows the Common Lisp @code{let} form:
+If any of the expressions are plain symbols, the loop is instead
+interpreted as a Loop Macro specification as described later.
+(This is not a restriction in practice, since a plain symbol
+in the above notation would simply access and throw away the
+value of a variable.)
+@end defmac
-@defspec lexical-let (bindings@dots{}) forms@dots{}
-This form is exactly like @code{let} except that the bindings it
-establishes are purely lexical. Lexical bindings are similar to
-local variables in a language like C: Only the code physically
-within the body of the @code{lexical-let} (after macro expansion)
-may refer to the bound variables.
+@defmac cl-do (spec@dots{}) (end-test [result@dots{}]) forms@dots{}
+This macro creates a general iterative loop. Each @var{spec} is
+of the form
@example
-(setq a 5)
-(defun foo (b) (+ a b))
-(let ((a 2)) (foo a))
- @result{} 4
-(lexical-let ((a 2)) (foo a))
- @result{} 7
+(@var{var} [@var{init} [@var{step}]])
@end example
-@noindent
-In this example, a regular @code{let} binding of @code{a} actually
-makes a temporary change to the global variable @code{a}, so @code{foo}
-is able to see the binding of @code{a} to 2. But @code{lexical-let}
-actually creates a distinct local variable @code{a} for use within its
-body, without any effect on the global variable of the same name.
+The loop works as follows: First, each @var{var} is bound to the
+associated @var{init} value as if by a @code{let} form. Then, in
+each iteration of the loop, the @var{end-test} is evaluated; if
+true, the loop is finished. Otherwise, the body @var{forms} are
+evaluated, then each @var{var} is set to the associated @var{step}
+expression (as if by a @code{cl-psetq} form) and the next iteration
+begins. Once the @var{end-test} becomes true, the @var{result}
+forms are evaluated (with the @var{var}s still bound to their
+values) to produce the result returned by @code{cl-do}.
-The most important use of lexical bindings is to create @dfn{closures}.
-A closure is a function object that refers to an outside lexical
-variable. For example:
+The entire @code{cl-do} loop is enclosed in an implicit @code{nil}
+block, so that you can use @code{(cl-return)} to break out of the
+loop at any time.
-@example
-(defun make-adder (n)
- (lexical-let ((n n))
- (function (lambda (m) (+ n m)))))
-(setq add17 (make-adder 17))
-(funcall add17 4)
- @result{} 21
-@end example
+If there are no @var{result} forms, the loop returns @code{nil}.
+If a given @var{var} has no @var{step} form, it is bound to its
+@var{init} value but not otherwise modified during the @code{cl-do}
+loop (unless the code explicitly modifies it); this case is just
+a shorthand for putting a @code{(let ((@var{var} @var{init})) @dots{})}
+around the loop. If @var{init} is also omitted it defaults to
+@code{nil}, and in this case a plain @samp{@var{var}} can be used
+in place of @samp{(@var{var})}, again following the analogy with
+@code{let}.
-@noindent
-The call @code{(make-adder 17)} returns a function object which adds
-17 to its argument. If @code{let} had been used instead of
-@code{lexical-let}, the function object would have referred to the
-global @code{n}, which would have been bound to 17 only during the
-call to @code{make-adder} itself.
+This example (from Steele) illustrates a loop that applies the
+function @code{f} to successive pairs of values from the lists
+@code{foo} and @code{bar}; it is equivalent to the call
+@code{(cl-mapcar 'f foo bar)}. Note that this loop has no body
+@var{forms} at all, performing all its work as side effects of
+the rest of the loop.
@example
-(defun make-counter ()
- (lexical-let ((n 0))
- (cl-function (lambda (&optional (m 1)) (cl-incf n m)))))
-(setq count-1 (make-counter))
-(funcall count-1 3)
- @result{} 3
-(funcall count-1 14)
- @result{} 17
-(setq count-2 (make-counter))
-(funcall count-2 5)
- @result{} 5
-(funcall count-1 2)
- @result{} 19
-(funcall count-2)
- @result{} 6
+(cl-do ((x foo (cdr x))
+ (y bar (cdr y))
+ (z nil (cons (f (car x) (car y)) z)))
+ ((or (null x) (null y))
+ (nreverse z)))
@end example
+@end defmac
-@noindent
-Here we see that each call to @code{make-counter} creates a distinct
-local variable @code{n}, which serves as a private counter for the
-function object that is returned.
-
-Closed-over lexical variables persist until the last reference to
-them goes away, just like all other Lisp objects. For example,
-@code{count-2} refers to a function object which refers to an
-instance of the variable @code{n}; this is the only reference
-to that variable, so after @code{(setq count-2 nil)} the garbage
-collector would be able to delete this instance of @code{n}.
-Of course, if a @code{lexical-let} does not actually create any
-closures, then the lexical variables are free as soon as the
-@code{lexical-let} returns.
+@defmac cl-do* (spec@dots{}) (end-test [result@dots{}]) forms@dots{}
+This is to @code{cl-do} what @code{let*} is to @code{let}. In
+particular, the initial values are bound as if by @code{let*}
+rather than @code{let}, and the steps are assigned as if by
+@code{setq} rather than @code{cl-psetq}.
-Many closures are used only during the extent of the bindings they
-refer to; these are known as ``downward funargs'' in Lisp parlance.
-When a closure is used in this way, regular Emacs Lisp dynamic
-bindings suffice and will be more efficient than @code{lexical-let}
-closures:
+Here is another way to write the above loop:
@example
-(defun add-to-list (x list)
- (mapcar (lambda (y) (+ x y))) list)
-(add-to-list 7 '(1 2 5))
- @result{} (8 9 12)
+(cl-do* ((xp foo (cdr xp))
+ (yp bar (cdr yp))
+ (x (car xp) (car xp))
+ (y (car yp) (car yp))
+ z)
+ ((or (null xp) (null yp))
+ (nreverse z))
+ (push (f x y) z))
@end example
+@end defmac
-@noindent
-Since this lambda is only used while @code{x} is still bound,
-it is not necessary to make a true closure out of it.
+@defmac cl-dolist (var list [result]) forms@dots{}
+This is exactly like the standard Emacs Lisp macro @code{dolist},
+but surrounds the loop with an implicit @code{nil} block.
+@end defmac
-You can use @code{defun} or @code{flet} inside a @code{lexical-let}
-to create a named closure. If several closures are created in the
-body of a single @code{lexical-let}, they all close over the same
-instance of the lexical variable.
+@defmac cl-dotimes (var count [result]) forms@dots{}
+This is exactly like the standard Emacs Lisp macro @code{dotimes},
+but surrounds the loop with an implicit @code{nil} block.
+The body is executed with @var{var} bound to the integers
+from zero (inclusive) to @var{count} (exclusive), in turn. Then
+@c FIXME lispref does not state this part explicitly, could move this there.
+the @code{result} form is evaluated with @var{var} bound to the total
+number of iterations that were done (i.e., @code{(max 0 @var{count})})
+to get the return value for the loop form.
+@end defmac
+
+@defmac cl-do-symbols (var [obarray [result]]) forms@dots{}
+This loop iterates over all interned symbols. If @var{obarray}
+is specified and is not @code{nil}, it loops over all symbols in
+that obarray. For each symbol, the body @var{forms} are evaluated
+with @var{var} bound to that symbol. The symbols are visited in
+an unspecified order. Afterward the @var{result} form, if any,
+is evaluated (with @var{var} bound to @code{nil}) to get the return
+value. The loop is surrounded by an implicit @code{nil} block.
+@end defmac
-The @code{lexical-let} form is an extension to Common Lisp. In
-true Common Lisp, all bindings are lexical unless declared otherwise.
-@end defspec
+@defmac cl-do-all-symbols (var [result]) forms@dots{}
+This is identical to @code{cl-do-symbols} except that the @var{obarray}
+argument is omitted; it always iterates over the default obarray.
+@end defmac
-@defspec lexical-let* (bindings@dots{}) forms@dots{}
-This form is just like @code{lexical-let}, except that the bindings
-are made sequentially in the manner of @code{let*}.
-@end defspec
+@xref{Mapping over Sequences}, for some more functions for
+iterating over vectors or lists.
-@node Function Bindings
-@subsection Function Bindings
+@node Loop Facility
+@section Loop Facility
@noindent
-These forms make @code{let}-like bindings to functions instead
-of variables.
-
-@defspec flet (bindings@dots{}) forms@dots{}
-This form establishes @code{let}-style bindings on the function
-cells of symbols rather than on the value cells. Each @var{binding}
-must be a list of the form @samp{(@var{name} @var{arglist}
-@var{forms}@dots{})}, which defines a function exactly as if
-it were a @code{cl-defun} form. The function @var{name} is defined
-accordingly for the duration of the body of the @code{flet}; then
-the old function definition, or lack thereof, is restored.
+A common complaint with Lisp's traditional looping constructs was
+that they were either too simple and limited, such as @code{dotimes}
+or @code{while}, or too unreadable and obscure, like Common Lisp's
+@code{do} loop.
-While @code{flet} in Common Lisp establishes a lexical binding of
-@var{name}, Emacs Lisp @code{flet} makes a dynamic binding. The
-result is that @code{flet} affects indirect calls to a function as
-well as calls directly inside the @code{flet} form itself.
+To remedy this, Common Lisp added a construct called the ``Loop
+Facility'' or ``@code{loop} macro'', with an easy-to-use but very
+powerful and expressive syntax.
-You can use @code{flet} to disable or modify the behavior of a
-function in a temporary fashion. This will even work on Emacs
-primitives, although note that some calls to primitive functions
-internal to Emacs are made without going through the symbol's
-function cell, and so will not be affected by @code{flet}. For
-example,
+@menu
+* Loop Basics:: The @code{cl-loop} macro, basic clause structure.
+* Loop Examples:: Working examples of the @code{cl-loop} macro.
+* For Clauses:: Clauses introduced by @code{for} or @code{as}.
+* Iteration Clauses:: @code{repeat}, @code{while}, @code{thereis}, etc.
+* Accumulation Clauses:: @code{collect}, @code{sum}, @code{maximize}, etc.
+* Other Clauses:: @code{with}, @code{if}, @code{initially}, @code{finally}.
+@end menu
-@example
-(flet ((message (&rest args) (push args saved-msgs)))
- (do-something))
-@end example
-
-This code attempts to replace the built-in function @code{message}
-with a function that simply saves the messages in a list rather
-than displaying them. The original definition of @code{message}
-will be restored after @code{do-something} exits. This code will
-work fine on messages generated by other Lisp code, but messages
-generated directly inside Emacs will not be caught since they make
-direct C-language calls to the message routines rather than going
-through the Lisp @code{message} function.
-
-@c Bug#411.
-Also note that many primitives (e.g. @code{+}) have special byte-compile
-handling. Attempts to redefine such functions using @code{flet} will
-fail if byte-compiled. In such cases, use @code{labels} instead.
-
-Functions defined by @code{flet} may use the full Common Lisp
-argument notation supported by @code{cl-defun}; also, the function
-body is enclosed in an implicit block as if by @code{cl-defun}.
-@xref{Program Structure}.
-@end defspec
-
-@defspec labels (bindings@dots{}) forms@dots{}
-The @code{labels} form is like @code{flet}, except that it
-makes lexical bindings of the function names rather than
-dynamic bindings. (In true Common Lisp, both @code{flet} and
-@code{labels} make lexical bindings of slightly different sorts;
-since Emacs Lisp is dynamically bound by default, it seemed
-more appropriate for @code{flet} also to use dynamic binding.
-The @code{labels} form, with its lexical binding, is fully
-compatible with Common Lisp.)
-
-Lexical scoping means that all references to the named
-functions must appear physically within the body of the
-@code{labels} form. References may appear both in the body
-@var{forms} of @code{labels} itself, and in the bodies of
-the functions themselves. Thus, @code{labels} can define
-local recursive functions, or mutually-recursive sets of
-functions.
-
-A ``reference'' to a function name is either a call to that
-function, or a use of its name quoted by @code{quote} or
-@code{function} to be passed on to, say, @code{mapcar}.
-@end defspec
-
-@node Macro Bindings
-@subsection Macro Bindings
+@node Loop Basics
+@subsection Loop Basics
@noindent
-These forms create local macros and ``symbol macros''.
+The @code{cl-loop} macro essentially creates a mini-language within
+Lisp that is specially tailored for describing loops. While this
+language is a little strange-looking by the standards of regular Lisp,
+it turns out to be very easy to learn and well-suited to its purpose.
-@defspec cl-macrolet (bindings@dots{}) forms@dots{}
-This form is analogous to @code{flet}, but for macros instead of
-functions. Each @var{binding} is a list of the same form as the
-arguments to @code{cl-defmacro} (i.e., a macro name, argument list,
-and macro-expander forms). The macro is defined accordingly for
-use within the body of the @code{cl-macrolet}.
+Since @code{cl-loop} is a macro, all parsing of the loop language
+takes place at byte-compile time; compiled @code{cl-loop}s are just
+as efficient as the equivalent @code{while} loops written longhand.
-Because of the nature of macros, @code{cl-macrolet} is lexically
-scoped even in Emacs Lisp: The @code{cl-macrolet} binding will
-affect only calls that appear physically within the body
-@var{forms}, possibly after expansion of other macros in the
-body.
-@end defspec
+@defmac cl-loop clauses@dots{}
+A loop construct consists of a series of @var{clause}s, each
+introduced by a symbol like @code{for} or @code{do}. Clauses
+are simply strung together in the argument list of @code{cl-loop},
+with minimal extra parentheses. The various types of clauses
+specify initializations, such as the binding of temporary
+variables, actions to be taken in the loop, stepping actions,
+and final cleanup.
-@defspec cl-symbol-macrolet (bindings@dots{}) forms@dots{}
-This form creates @dfn{symbol macros}, which are macros that look
-like variable references rather than function calls. Each
-@var{binding} is a list @samp{(@var{var} @var{expansion})};
-any reference to @var{var} within the body @var{forms} is
-replaced by @var{expansion}.
+Common Lisp specifies a certain general order of clauses in a
+loop:
@example
-(setq bar '(5 . 9))
-(cl-symbol-macrolet ((foo (car bar)))
- (cl-incf foo))
-bar
- @result{} (6 . 9)
+(loop @var{name-clause}
+ @var{var-clauses}@dots{}
+ @var{action-clauses}@dots{})
@end example
-A @code{setq} of a symbol macro is treated the same as a @code{setf}.
-I.e., @code{(setq foo 4)} in the above would be equivalent to
-@code{(setf foo 4)}, which in turn expands to @code{(setf (car bar) 4)}.
+The @var{name-clause} optionally gives a name to the implicit
+block that surrounds the loop. By default, the implicit block
+is named @code{nil}. The @var{var-clauses} specify what
+variables should be bound during the loop, and how they should
+be modified or iterated throughout the course of the loop. The
+@var{action-clauses} are things to be done during the loop, such
+as computing, collecting, and returning values.
-Likewise, a @code{let} or @code{let*} binding a symbol macro is
-treated like a @code{letf} or @code{cl-letf*}. This differs from true
-Common Lisp, where the rules of lexical scoping cause a @code{let}
-binding to shadow a @code{cl-symbol-macrolet} binding. In this package,
-only @code{lexical-let} and @code{lexical-let*} will shadow a symbol
-macro.
+The Emacs version of the @code{cl-loop} macro is less restrictive about
+the order of clauses, but things will behave most predictably if
+you put the variable-binding clauses @code{with}, @code{for}, and
+@code{repeat} before the action clauses. As in Common Lisp,
+@code{initially} and @code{finally} clauses can go anywhere.
-There is no analogue of @code{defmacro} for symbol macros; all symbol
-macros are local. A typical use of @code{cl-symbol-macrolet} is in the
-expansion of another macro:
+Loops generally return @code{nil} by default, but you can cause
+them to return a value by using an accumulation clause like
+@code{collect}, an end-test clause like @code{always}, or an
+explicit @code{return} clause to jump out of the implicit block.
+(Because the loop body is enclosed in an implicit block, you can
+also use regular Lisp @code{cl-return} or @code{cl-return-from} to
+break out of the loop.)
+@end defmac
-@example
-(cl-defmacro my-dolist ((x list) &rest body)
- (let ((var (gensym)))
- (list 'cl-loop 'for var 'on list 'do
- (cl-list* 'cl-symbol-macrolet
- (list (list x (list 'car var)))
- body))))
+The following sections give some examples of the loop macro in
+action, and describe the particular loop clauses in great detail.
+Consult the second edition of Steele for additional discussion
+and examples.
-(setq mylist '(1 2 3 4))
-(my-dolist (x mylist) (cl-incf x))
-mylist
- @result{} (2 3 4 5)
-@end example
+@node Loop Examples
+@subsection Loop Examples
@noindent
-In this example, the @code{my-dolist} macro is similar to @code{dolist}
-(@pxref{Iteration}) except that the variable @code{x} becomes a true
-reference onto the elements of the list. The @code{my-dolist} call
-shown here expands to
+Before listing the full set of clauses that are allowed, let's
+look at a few example loops just to get a feel for the @code{cl-loop}
+language.
@example
-(cl-loop for G1234 on mylist do
- (cl-symbol-macrolet ((x (car G1234)))
- (cl-incf x)))
+(cl-loop for buf in (buffer-list)
+ collect (buffer-file-name buf))
@end example
@noindent
-which in turn expands to
+This loop iterates over all Emacs buffers, using the list
+returned by @code{buffer-list}. For each buffer @var{buf},
+it calls @code{buffer-file-name} and collects the results into
+a list, which is then returned from the @code{cl-loop} construct.
+The result is a list of the file names of all the buffers in
+Emacs's memory. The words @code{for}, @code{in}, and @code{collect}
+are reserved words in the @code{cl-loop} language.
@example
-(cl-loop for G1234 on mylist do (cl-incf (car G1234)))
+(cl-loop repeat 20 do (insert "Yowsa\n"))
@end example
-@xref{Loop Facility}, for a description of the @code{cl-loop} macro.
-This package defines a nonstandard @code{in-ref} loop clause that
-works much like @code{my-dolist}.
-@end defspec
-
-@node Conditionals
-@section Conditionals
-
@noindent
-These conditional forms augment Emacs Lisp's simple @code{if},
-@code{and}, @code{or}, and @code{cond} forms.
-
-@defspec cl-case keyform clause@dots{}
-This macro evaluates @var{keyform}, then compares it with the key
-values listed in the various @var{clause}s. Whichever clause matches
-the key is executed; comparison is done by @code{eql}. If no clause
-matches, the @code{cl-case} form returns @code{nil}. The clauses are
-of the form
+This loop inserts the phrase ``Yowsa'' twenty times in the
+current buffer.
@example
-(@var{keylist} @var{body-forms}@dots{})
+(cl-loop until (eobp) do (munch-line) (forward-line 1))
@end example
@noindent
-where @var{keylist} is a list of key values. If there is exactly
-one value, and it is not a cons cell or the symbol @code{nil} or
-@code{t}, then it can be used by itself as a @var{keylist} without
-being enclosed in a list. All key values in the @code{cl-case} form
-must be distinct. The final clauses may use @code{t} in place of
-a @var{keylist} to indicate a default clause that should be taken
-if none of the other clauses match. (The symbol @code{otherwise}
-is also recognized in place of @code{t}. To make a clause that
-matches the actual symbol @code{t}, @code{nil}, or @code{otherwise},
-enclose the symbol in a list.)
-
-For example, this expression reads a keystroke, then does one of
-four things depending on whether it is an @samp{a}, a @samp{b},
-a @key{RET} or @kbd{C-j}, or anything else.
+This loop calls @code{munch-line} on every line until the end
+of the buffer. If point is already at the end of the buffer,
+the loop exits immediately.
@example
-(cl-case (read-char)
- (?a (do-a-thing))
- (?b (do-b-thing))
- ((?\r ?\n) (do-ret-thing))
- (t (do-other-thing)))
+(cl-loop do (munch-line) until (eobp) do (forward-line 1))
@end example
-@end defspec
-
-@defspec cl-ecase keyform clause@dots{}
-This macro is just like @code{cl-case}, except that if the key does
-not match any of the clauses, an error is signaled rather than
-simply returning @code{nil}.
-@end defspec
-@defspec cl-typecase keyform clause@dots{}
-This macro is a version of @code{cl-case} that checks for types
-rather than values. Each @var{clause} is of the form
-@samp{(@var{type} @var{body}...)}. @xref{Type Predicates},
-for a description of type specifiers. For example,
+@noindent
+This loop is similar to the above one, except that @code{munch-line}
+is always called at least once.
@example
-(cl-typecase x
- (integer (munch-integer x))
- (float (munch-float x))
- (string (munch-integer (string-to-int x)))
- (t (munch-anything x)))
+(cl-loop for x from 1 to 100
+ for y = (* x x)
+ until (>= y 729)
+ finally return (list x (= y 729)))
@end example
-The type specifier @code{t} matches any type of object; the word
-@code{otherwise} is also allowed. To make one clause match any of
-several types, use an @code{(or ...)} type specifier.
-@end defspec
+@noindent
+This more complicated loop searches for a number @code{x} whose
+square is 729. For safety's sake it only examines @code{x}
+values up to 100; dropping the phrase @samp{to 100} would
+cause the loop to count upwards with no limit. The second
+@code{for} clause defines @code{y} to be the square of @code{x}
+within the loop; the expression after the @code{=} sign is
+reevaluated each time through the loop. The @code{until}
+clause gives a condition for terminating the loop, and the
+@code{finally} clause says what to do when the loop finishes.
+(This particular example was written less concisely than it
+could have been, just for the sake of illustration.)
-@defspec cl-etypecase keyform clause@dots{}
-This macro is just like @code{cl-typecase}, except that if the key does
-not match any of the clauses, an error is signaled rather than
-simply returning @code{nil}.
-@end defspec
+Note that even though this loop contains three clauses (two
+@code{for}s and an @code{until}) that would have been enough to
+define loops all by themselves, it still creates a single loop
+rather than some sort of triple-nested loop. You must explicitly
+nest your @code{cl-loop} constructs if you want nested loops.
-@node Blocks and Exits
-@section Blocks and Exits
+@node For Clauses
+@subsection For Clauses
@noindent
-Common Lisp @dfn{blocks} provide a non-local exit mechanism very
-similar to @code{catch} and @code{throw}, but lexically rather than
-dynamically scoped. This package actually implements @code{cl-block}
-in terms of @code{catch}; however, the lexical scoping allows the
-optimizing byte-compiler to omit the costly @code{catch} step if the
-body of the block does not actually @code{cl-return-from} the block.
-
-@defspec cl-block name forms@dots{}
-The @var{forms} are evaluated as if by a @code{progn}. However,
-if any of the @var{forms} execute @code{(cl-return-from @var{name})},
-they will jump out and return directly from the @code{cl-block} form.
-The @code{cl-block} returns the result of the last @var{form} unless
-a @code{cl-return-from} occurs.
+Most loops are governed by one or more @code{for} clauses.
+A @code{for} clause simultaneously describes variables to be
+bound, how those variables are to be stepped during the loop,
+and usually an end condition based on those variables.
-The @code{cl-block}/@code{cl-return-from} mechanism is quite similar to
-the @code{catch}/@code{throw} mechanism. The main differences are
-that block @var{name}s are unevaluated symbols, rather than forms
-(such as quoted symbols) which evaluate to a tag at run-time; and
-also that blocks are lexically scoped whereas @code{catch}/@code{throw}
-are dynamically scoped. This means that functions called from the
-body of a @code{catch} can also @code{throw} to the @code{catch},
-but the @code{cl-return-from} referring to a block name must appear
-physically within the @var{forms} that make up the body of the block.
-They may not appear within other called functions, although they may
-appear within macro expansions or @code{lambda}s in the body. Block
-names and @code{catch} names form independent name-spaces.
+The word @code{as} is a synonym for the word @code{for}. This
+word is followed by a variable name, then a word like @code{from}
+or @code{across} that describes the kind of iteration desired.
+In Common Lisp, the phrase @code{being the} sometimes precedes
+the type of iteration; in this package both @code{being} and
+@code{the} are optional. The word @code{each} is a synonym
+for @code{the}, and the word that follows it may be singular
+or plural: @samp{for x being the elements of y} or
+@samp{for x being each element of y}. Which form you use
+is purely a matter of style.
-In true Common Lisp, @code{defun} and @code{defmacro} surround
-the function or expander bodies with implicit blocks with the
-same name as the function or macro. This does not occur in Emacs
-Lisp, but this package provides @code{cl-defun} and @code{cl-defmacro}
-forms which do create the implicit block.
+The variable is bound around the loop as if by @code{let}:
-The Common Lisp looping constructs defined by this package,
-such as @code{cl-loop} and @code{cl-dolist}, also create implicit blocks
-just as in Common Lisp.
+@example
+(setq i 'happy)
+(cl-loop for i from 1 to 10 do (do-something-with i))
+i
+ @result{} happy
+@end example
-Because they are implemented in terms of Emacs Lisp @code{catch}
-and @code{throw}, blocks have the same overhead as actual
-@code{catch} constructs (roughly two function calls). However,
-the optimizing byte compiler will optimize away the @code{catch}
-if the block does
-not in fact contain any @code{cl-return} or @code{cl-return-from} calls
-that jump to it. This means that @code{cl-do} loops and @code{cl-defun}
-functions which don't use @code{cl-return} don't pay the overhead to
-support it.
-@end defspec
-
-@defspec cl-return-from name [result]
-This macro returns from the block named @var{name}, which must be
-an (unevaluated) symbol. If a @var{result} form is specified, it
-is evaluated to produce the result returned from the @code{block}.
-Otherwise, @code{nil} is returned.
-@end defspec
+@table @code
+@item for @var{var} from @var{expr1} to @var{expr2} by @var{expr3}
+This type of @code{for} clause creates a counting loop. Each of
+the three sub-terms is optional, though there must be at least one
+term so that the clause is marked as a counting clause.
-@defspec cl-return [result]
-This macro is exactly like @code{(cl-return-from nil @var{result})}.
-Common Lisp loops like @code{cl-do} and @code{cl-dolist} implicitly enclose
-themselves in @code{nil} blocks.
-@end defspec
+The three expressions are the starting value, the ending value, and
+the step value, respectively, of the variable. The loop counts
+upwards by default (@var{expr3} must be positive), from @var{expr1}
+to @var{expr2} inclusively. If you omit the @code{from} term, the
+loop counts from zero; if you omit the @code{to} term, the loop
+counts forever without stopping (unless stopped by some other
+loop clause, of course); if you omit the @code{by} term, the loop
+counts in steps of one.
-@node Iteration
-@section Iteration
+You can replace the word @code{from} with @code{upfrom} or
+@code{downfrom} to indicate the direction of the loop. Likewise,
+you can replace @code{to} with @code{upto} or @code{downto}.
+For example, @samp{for x from 5 downto 1} executes five times
+with @code{x} taking on the integers from 5 down to 1 in turn.
+Also, you can replace @code{to} with @code{below} or @code{above},
+which are like @code{upto} and @code{downto} respectively except
+that they are exclusive rather than inclusive limits:
-@noindent
-The macros described here provide more sophisticated, high-level
-looping constructs to complement Emacs Lisp's basic @code{while}
-loop.
+@example
+(cl-loop for x to 10 collect x)
+ @result{} (0 1 2 3 4 5 6 7 8 9 10)
+(cl-loop for x below 10 collect x)
+ @result{} (0 1 2 3 4 5 6 7 8 9)
+@end example
-@defspec cl-loop forms@dots{}
-The @code{CL} package supports both the simple, old-style meaning of
-@code{loop} and the extremely powerful and flexible feature known as
-the @dfn{Loop Facility} or @dfn{Loop Macro}. This more advanced
-facility is discussed in the following section; @pxref{Loop Facility}.
-The simple form of @code{loop} is described here.
+The @code{by} value is always positive, even for downward-counting
+loops. Some sort of @code{from} value is required for downward
+loops; @samp{for x downto 5} is not a valid loop clause all by
+itself.
-If @code{cl-loop} is followed by zero or more Lisp expressions,
-then @code{(cl-loop @var{exprs}@dots{})} simply creates an infinite
-loop executing the expressions over and over. The loop is
-enclosed in an implicit @code{nil} block. Thus,
+@item for @var{var} in @var{list} by @var{function}
+This clause iterates @var{var} over all the elements of @var{list},
+in turn. If you specify the @code{by} term, then @var{function}
+is used to traverse the list instead of @code{cdr}; it must be a
+function taking one argument. For example:
@example
-(cl-loop (foo) (if (no-more) (return 72)) (bar))
+(cl-loop for x in '(1 2 3 4 5 6) collect (* x x))
+ @result{} (1 4 9 16 25 36)
+(cl-loop for x in '(1 2 3 4 5 6) by 'cddr collect (* x x))
+ @result{} (1 9 25)
@end example
-@noindent
-is exactly equivalent to
+@item for @var{var} on @var{list} by @var{function}
+This clause iterates @var{var} over all the cons cells of @var{list}.
@example
-(cl-block nil (while t (foo) (if (no-more) (return 72)) (bar)))
+(cl-loop for x on '(1 2 3 4) collect x)
+ @result{} ((1 2 3 4) (2 3 4) (3 4) (4))
@end example
-If any of the expressions are plain symbols, the loop is instead
-interpreted as a Loop Macro specification as described later.
-(This is not a restriction in practice, since a plain symbol
-in the above notation would simply access and throw away the
-value of a variable.)
-@end defspec
-
-@defspec cl-do (spec@dots{}) (end-test [result@dots{}]) forms@dots{}
-This macro creates a general iterative loop. Each @var{spec} is
-of the form
+With @code{by}, there is no real reason that the @code{on} expression
+must be a list. For example:
@example
-(@var{var} [@var{init} [@var{step}]])
+(cl-loop for x on first-animal by 'next-animal collect x)
@end example
-The loop works as follows: First, each @var{var} is bound to the
-associated @var{init} value as if by a @code{let} form. Then, in
-each iteration of the loop, the @var{end-test} is evaluated; if
-true, the loop is finished. Otherwise, the body @var{forms} are
-evaluated, then each @var{var} is set to the associated @var{step}
-expression (as if by a @code{cl-psetq} form) and the next iteration
-begins. Once the @var{end-test} becomes true, the @var{result}
-forms are evaluated (with the @var{var}s still bound to their
-values) to produce the result returned by @code{cl-do}.
-
-The entire @code{cl-do} loop is enclosed in an implicit @code{nil}
-block, so that you can use @code{(cl-return)} to break out of the
-loop at any time.
-
-If there are no @var{result} forms, the loop returns @code{nil}.
-If a given @var{var} has no @var{step} form, it is bound to its
-@var{init} value but not otherwise modified during the @code{cl-do}
-loop (unless the code explicitly modifies it); this case is just
-a shorthand for putting a @code{(let ((@var{var} @var{init})) @dots{})}
-around the loop. If @var{init} is also omitted it defaults to
-@code{nil}, and in this case a plain @samp{@var{var}} can be used
-in place of @samp{(@var{var})}, again following the analogy with
-@code{let}.
+@noindent
+where @code{(next-animal x)} takes an ``animal'' @var{x} and returns
+the next in the (assumed) sequence of animals, or @code{nil} if
+@var{x} was the last animal in the sequence.
-This example (from Steele) illustrates a loop which applies the
-function @code{f} to successive pairs of values from the lists
-@code{foo} and @code{bar}; it is equivalent to the call
-@code{(cl-mapcar 'f foo bar)}. Note that this loop has no body
-@var{forms} at all, performing all its work as side effects of
-the rest of the loop.
+@item for @var{var} in-ref @var{list} by @var{function}
+This is like a regular @code{in} clause, but @var{var} becomes
+a @code{setf}-able ``reference'' onto the elements of the list
+rather than just a temporary variable. For example,
@example
-(cl-do ((x foo (cdr x))
- (y bar (cdr y))
- (z nil (cons (f (car x) (car y)) z)))
- ((or (null x) (null y))
- (nreverse z)))
+(cl-loop for x in-ref my-list do (cl-incf x))
@end example
-@end defspec
-@defspec cl-do* (spec@dots{}) (end-test [result@dots{}]) forms@dots{}
-This is to @code{cl-do} what @code{let*} is to @code{let}. In
-particular, the initial values are bound as if by @code{let*}
-rather than @code{let}, and the steps are assigned as if by
-@code{setq} rather than @code{cl-psetq}.
+@noindent
+increments every element of @code{my-list} in place. This clause
+is an extension to standard Common Lisp.
-Here is another way to write the above loop:
+@item for @var{var} across @var{array}
+This clause iterates @var{var} over all the elements of @var{array},
+which may be a vector or a string.
@example
-(cl-do* ((xp foo (cdr xp))
- (yp bar (cdr yp))
- (x (car xp) (car xp))
- (y (car yp) (car yp))
- z)
- ((or (null xp) (null yp))
- (nreverse z))
- (push (f x y) z))
+(cl-loop for x across "aeiou"
+ do (use-vowel (char-to-string x)))
@end example
-@end defspec
-
-@defspec cl-dolist (var list [result]) forms@dots{}
-This is a more specialized loop which iterates across the elements
-of a list. @var{list} should evaluate to a list; the body @var{forms}
-are executed with @var{var} bound to each element of the list in
-turn. Finally, the @var{result} form (or @code{nil}) is evaluated
-with @var{var} bound to @code{nil} to produce the result returned by
-the loop. Unlike with Emacs's built in @code{dolist}, the loop is
-surrounded by an implicit @code{nil} block.
-@end defspec
-
-@defspec cl-dotimes (var count [result]) forms@dots{}
-This is a more specialized loop which iterates a specified number
-of times. The body is executed with @var{var} bound to the integers
-from zero (inclusive) to @var{count} (exclusive), in turn. Then
-the @code{result} form is evaluated with @var{var} bound to the total
-number of iterations that were done (i.e., @code{(max 0 @var{count})})
-to get the return value for the loop form. Unlike with Emacs's built in
-@code{dolist}, the loop is surrounded by an implicit @code{nil} block.
-@end defspec
-
-@defspec cl-do-symbols (var [obarray [result]]) forms@dots{}
-This loop iterates over all interned symbols. If @var{obarray}
-is specified and is not @code{nil}, it loops over all symbols in
-that obarray. For each symbol, the body @var{forms} are evaluated
-with @var{var} bound to that symbol. The symbols are visited in
-an unspecified order. Afterward the @var{result} form, if any,
-is evaluated (with @var{var} bound to @code{nil}) to get the return
-value. The loop is surrounded by an implicit @code{nil} block.
-@end defspec
-@defspec cl-do-all-symbols (var [result]) forms@dots{}
-This is identical to @code{cl-do-symbols} except that the @var{obarray}
-argument is omitted; it always iterates over the default obarray.
-@end defspec
+@item for @var{var} across-ref @var{array}
+This clause iterates over an array, with @var{var} a @code{setf}-able
+reference onto the elements; see @code{in-ref} above.
-@xref{Mapping over Sequences}, for some more functions for
-iterating over vectors or lists.
+@item for @var{var} being the elements of @var{sequence}
+This clause iterates over the elements of @var{sequence}, which may
+be a list, vector, or string. Since the type must be determined
+at run-time, this is somewhat less efficient than @code{in} or
+@code{across}. The clause may be followed by the additional term
+@samp{using (index @var{var2})} to cause @var{var2} to be bound to
+the successive indices (starting at 0) of the elements.
-@node Loop Facility
-@section Loop Facility
+This clause type is taken from older versions of the @code{loop} macro,
+and is not present in modern Common Lisp. The @samp{using (sequence @dots{})}
+term of the older macros is not supported.
-@noindent
-A common complaint with Lisp's traditional looping constructs is
-that they are either too simple and limited, such as Common Lisp's
-@code{dotimes} or Emacs Lisp's @code{while}, or too unreadable and
-obscure, like Common Lisp's @code{do} loop.
+@item for @var{var} being the elements of-ref @var{sequence}
+This clause iterates over a sequence, with @var{var} a @code{setf}-able
+reference onto the elements; see @code{in-ref} above.
-To remedy this, recent versions of Common Lisp have added a new
-construct called the ``Loop Facility'' or ``@code{loop} macro'',
-with an easy-to-use but very powerful and expressive syntax.
+@item for @var{var} being the symbols [of @var{obarray}]
+This clause iterates over symbols, either over all interned symbols
+or over all symbols in @var{obarray}. The loop is executed with
+@var{var} bound to each symbol in turn. The symbols are visited in
+an unspecified order.
-@menu
-* Loop Basics:: @code{cl-loop} macro, basic clause structure.
-* Loop Examples:: Working examples of @code{cl-loop} macro.
-* For Clauses:: Clauses introduced by @code{for} or @code{as}.
-* Iteration Clauses:: @code{repeat}, @code{while}, @code{thereis}, etc.
-* Accumulation Clauses:: @code{collect}, @code{sum}, @code{maximize}, etc.
-* Other Clauses:: @code{with}, @code{if}, @code{initially}, @code{finally}.
-@end menu
+As an example,
-@node Loop Basics
-@subsection Loop Basics
+@example
+(cl-loop for sym being the symbols
+ when (fboundp sym)
+ when (string-match "^map" (symbol-name sym))
+ collect sym)
+@end example
@noindent
-The @code{cl-loop} macro essentially creates a mini-language within
-Lisp that is specially tailored for describing loops. While this
-language is a little strange-looking by the standards of regular Lisp,
-it turns out to be very easy to learn and well-suited to its purpose.
+returns a list of all the functions whose names begin with @samp{map}.
-Since @code{cl-loop} is a macro, all parsing of the loop language
-takes place at byte-compile time; compiled @code{cl-loop}s are just
-as efficient as the equivalent @code{while} loops written longhand.
+The Common Lisp words @code{external-symbols} and @code{present-symbols}
+are also recognized but are equivalent to @code{symbols} in Emacs Lisp.
-@defspec cl-loop clauses@dots{}
-A loop construct consists of a series of @var{clause}s, each
-introduced by a symbol like @code{for} or @code{do}. Clauses
-are simply strung together in the argument list of @code{cl-loop},
-with minimal extra parentheses. The various types of clauses
-specify initializations, such as the binding of temporary
-variables, actions to be taken in the loop, stepping actions,
-and final cleanup.
+Due to a minor implementation restriction, it will not work to have
+more than one @code{for} clause iterating over symbols, hash tables,
+keymaps, overlays, or intervals in a given @code{cl-loop}. Fortunately,
+it would rarely if ever be useful to do so. It @emph{is} valid to mix
+one of these types of clauses with other clauses like @code{for @dots{} to}
+or @code{while}.
-Common Lisp specifies a certain general order of clauses in a
-loop:
+@item for @var{var} being the hash-keys of @var{hash-table}
+@itemx for @var{var} being the hash-values of @var{hash-table}
+This clause iterates over the entries in @var{hash-table} with
+@var{var} bound to each key, or value. A @samp{using} clause can bind
+a second variable to the opposite part.
@example
-(cl-loop @var{name-clause}
- @var{var-clauses}@dots{}
- @var{action-clauses}@dots{})
+(cl-loop for k being the hash-keys of h
+ using (hash-values v)
+ do
+ (message "key %S -> value %S" k v))
@end example
-The @var{name-clause} optionally gives a name to the implicit
-block that surrounds the loop. By default, the implicit block
-is named @code{nil}. The @var{var-clauses} specify what
-variables should be bound during the loop, and how they should
-be modified or iterated throughout the course of the loop. The
-@var{action-clauses} are things to be done during the loop, such
-as computing, collecting, and returning values.
-
-The Emacs version of the @code{cl-loop} macro is less restrictive about
-the order of clauses, but things will behave most predictably if
-you put the variable-binding clauses @code{with}, @code{for}, and
-@code{repeat} before the action clauses. As in Common Lisp,
-@code{initially} and @code{finally} clauses can go anywhere.
+@item for @var{var} being the key-codes of @var{keymap}
+@itemx for @var{var} being the key-bindings of @var{keymap}
+This clause iterates over the entries in @var{keymap}.
+The iteration does not enter nested keymaps but does enter inherited
+(parent) keymaps.
+A @code{using} clause can access both the codes and the bindings
+together.
-Loops generally return @code{nil} by default, but you can cause
-them to return a value by using an accumulation clause like
-@code{collect}, an end-test clause like @code{always}, or an
-explicit @code{return} clause to jump out of the implicit block.
-(Because the loop body is enclosed in an implicit block, you can
-also use regular Lisp @code{cl-return} or @code{cl-return-from} to
-break out of the loop.)
-@end defspec
+@example
+(cl-loop for c being the key-codes of (current-local-map)
+ using (key-bindings b)
+ do
+ (message "key %S -> binding %S" c b))
+@end example
-The following sections give some examples of the Loop Macro in
-action, and describe the particular loop clauses in great detail.
-Consult the second edition of Steele's @dfn{Common Lisp, the Language},
-for additional discussion and examples of the @code{loop} macro.
-@node Loop Examples
-@subsection Loop Examples
+@item for @var{var} being the key-seqs of @var{keymap}
+This clause iterates over all key sequences defined by @var{keymap}
+and its nested keymaps, where @var{var} takes on values which are
+vectors. The strings or vectors
+are reused for each iteration, so you must copy them if you wish to keep
+them permanently. You can add a @samp{using (key-bindings @dots{})}
+clause to get the command bindings as well.
-@noindent
-Before listing the full set of clauses that are allowed, let's
-look at a few example loops just to get a feel for the @code{cl-loop}
-language.
+@item for @var{var} being the overlays [of @var{buffer}] @dots{}
+This clause iterates over the ``overlays'' of a buffer
+(the clause @code{extents} is synonymous
+with @code{overlays}). If the @code{of} term is omitted, the current
+buffer is used.
+This clause also accepts optional @samp{from @var{pos}} and
+@samp{to @var{pos}} terms, limiting the clause to overlays which
+overlap the specified region.
-@example
-(cl-loop for buf in (buffer-list)
- collect (buffer-file-name buf))
-@end example
+@item for @var{var} being the intervals [of @var{buffer}] @dots{}
+This clause iterates over all intervals of a buffer with constant
+text properties. The variable @var{var} will be bound to conses
+of start and end positions, where one start position is always equal
+to the previous end position. The clause allows @code{of},
+@code{from}, @code{to}, and @code{property} terms, where the latter
+term restricts the search to just the specified property. The
+@code{of} term may specify either a buffer or a string.
-@noindent
-This loop iterates over all Emacs buffers, using the list
-returned by @code{buffer-list}. For each buffer @var{buf},
-it calls @code{buffer-file-name} and collects the results into
-a list, which is then returned from the @code{cl-loop} construct.
-The result is a list of the file names of all the buffers in
-Emacs's memory. The words @code{for}, @code{in}, and @code{collect}
-are reserved words in the @code{cl-loop} language.
+@item for @var{var} being the frames
+This clause iterates over all Emacs frames. The clause @code{screens} is
+a synonym for @code{frames}. The frames are visited in
+@code{next-frame} order starting from @code{selected-frame}.
-@example
-(cl-loop repeat 20 do (insert "Yowsa\n"))
-@end example
+@item for @var{var} being the windows [of @var{frame}]
+This clause iterates over the windows (in the Emacs sense) of
+the current frame, or of the specified @var{frame}. It visits windows
+in @code{next-window} order starting from @code{selected-window}
+(or @code{frame-selected-window} if you specify @var{frame}).
+This clause treats the minibuffer window in the same way as
+@code{next-window} does. For greater flexibility, consider using
+@code{walk-windows} instead.
-@noindent
-This loop inserts the phrase ``Yowsa'' twenty times in the
-current buffer.
+@item for @var{var} being the buffers
+This clause iterates over all buffers in Emacs. It is equivalent
+to @samp{for @var{var} in (buffer-list)}.
+
+@item for @var{var} = @var{expr1} then @var{expr2}
+This clause does a general iteration. The first time through
+the loop, @var{var} will be bound to @var{expr1}. On the second
+and successive iterations it will be set by evaluating @var{expr2}
+(which may refer to the old value of @var{var}). For example,
+these two loops are effectively the same:
@example
-(cl-loop until (eobp) do (munch-line) (forward-line 1))
+(cl-loop for x on my-list by 'cddr do @dots{})
+(cl-loop for x = my-list then (cddr x) while x do @dots{})
@end example
-@noindent
-This loop calls @code{munch-line} on every line until the end
-of the buffer. If point is already at the end of the buffer,
-the loop exits immediately.
+Note that this type of @code{for} clause does not imply any sort
+of terminating condition; the above example combines it with a
+@code{while} clause to tell when to end the loop.
+
+If you omit the @code{then} term, @var{expr1} is used both for
+the initial setting and for successive settings:
@example
-(cl-loop do (munch-line) until (eobp) do (forward-line 1))
+(cl-loop for x = (random) when (> x 0) return x)
@end example
@noindent
-This loop is similar to the above one, except that @code{munch-line}
-is always called at least once.
+This loop keeps taking random numbers from the @code{(random)}
+function until it gets a positive one, which it then returns.
+@end table
+
+If you include several @code{for} clauses in a row, they are
+treated sequentially (as if by @code{let*} and @code{setq}).
+You can instead use the word @code{and} to link the clauses,
+in which case they are processed in parallel (as if by @code{let}
+and @code{cl-psetq}).
@example
-(cl-loop for x from 1 to 100
- for y = (* x x)
- until (>= y 729)
- finally return (list x (= y 729)))
+(cl-loop for x below 5 for y = nil then x collect (list x y))
+ @result{} ((0 nil) (1 1) (2 2) (3 3) (4 4))
+(cl-loop for x below 5 and y = nil then x collect (list x y))
+ @result{} ((0 nil) (1 0) (2 1) (3 2) (4 3))
@end example
@noindent
-This more complicated loop searches for a number @code{x} whose
-square is 729. For safety's sake it only examines @code{x}
-values up to 100; dropping the phrase @samp{to 100} would
-cause the loop to count upwards with no limit. The second
-@code{for} clause defines @code{y} to be the square of @code{x}
-within the loop; the expression after the @code{=} sign is
-reevaluated each time through the loop. The @code{until}
-clause gives a condition for terminating the loop, and the
-@code{finally} clause says what to do when the loop finishes.
-(This particular example was written less concisely than it
-could have been, just for the sake of illustration.)
-
-Note that even though this loop contains three clauses (two
-@code{for}s and an @code{until}) that would have been enough to
-define loops all by themselves, it still creates a single loop
-rather than some sort of triple-nested loop. You must explicitly
-nest your @code{cl-loop} constructs if you want nested loops.
-
-@node For Clauses
-@subsection For Clauses
+In the first loop, @code{y} is set based on the value of @code{x}
+that was just set by the previous clause; in the second loop,
+@code{x} and @code{y} are set simultaneously so @code{y} is set
+based on the value of @code{x} left over from the previous time
+through the loop.
-@noindent
-Most loops are governed by one or more @code{for} clauses.
-A @code{for} clause simultaneously describes variables to be
-bound, how those variables are to be stepped during the loop,
-and usually an end condition based on those variables.
+Another feature of the @code{cl-loop} macro is @emph{destructuring},
+similar in concept to the destructuring provided by @code{defmacro}
+(@pxref{Argument Lists}).
+The @var{var} part of any @code{for} clause can be given as a list
+of variables instead of a single variable. The values produced
+during loop execution must be lists; the values in the lists are
+stored in the corresponding variables.
-The word @code{as} is a synonym for the word @code{for}. This
-word is followed by a variable name, then a word like @code{from}
-or @code{across} that describes the kind of iteration desired.
-In Common Lisp, the phrase @code{being the} sometimes precedes
-the type of iteration; in this package both @code{being} and
-@code{the} are optional. The word @code{each} is a synonym
-for @code{the}, and the word that follows it may be singular
-or plural: @samp{for x being the elements of y} or
-@samp{for x being each element of y}. Which form you use
-is purely a matter of style.
+@example
+(cl-loop for (x y) in '((2 3) (4 5) (6 7)) collect (+ x y))
+ @result{} (5 9 13)
+@end example
-The variable is bound around the loop as if by @code{let}:
+In loop destructuring, if there are more values than variables
+the trailing values are ignored, and if there are more variables
+than values the trailing variables get the value @code{nil}.
+If @code{nil} is used as a variable name, the corresponding
+values are ignored. Destructuring may be nested, and dotted
+lists of variables like @code{(x . y)} are allowed, so for example
+to process an alist
@example
-(setq i 'happy)
-(cl-loop for i from 1 to 10 do (do-something-with i))
-i
- @result{} happy
+(cl-loop for (key . value) in '((a . 1) (b . 2))
+ collect value)
+ @result{} (1 2)
@end example
-@table @code
-@item for @var{var} from @var{expr1} to @var{expr2} by @var{expr3}
-This type of @code{for} clause creates a counting loop. Each of
-the three sub-terms is optional, though there must be at least one
-term so that the clause is marked as a counting clause.
+@node Iteration Clauses
+@subsection Iteration Clauses
-The three expressions are the starting value, the ending value, and
-the step value, respectively, of the variable. The loop counts
-upwards by default (@var{expr3} must be positive), from @var{expr1}
-to @var{expr2} inclusively. If you omit the @code{from} term, the
-loop counts from zero; if you omit the @code{to} term, the loop
-counts forever without stopping (unless stopped by some other
-loop clause, of course); if you omit the @code{by} term, the loop
-counts in steps of one.
+@noindent
+Aside from @code{for} clauses, there are several other loop clauses
+that control the way the loop operates. They might be used by
+themselves, or in conjunction with one or more @code{for} clauses.
-You can replace the word @code{from} with @code{upfrom} or
-@code{downfrom} to indicate the direction of the loop. Likewise,
-you can replace @code{to} with @code{upto} or @code{downto}.
-For example, @samp{for x from 5 downto 1} executes five times
-with @code{x} taking on the integers from 5 down to 1 in turn.
-Also, you can replace @code{to} with @code{below} or @code{above},
-which are like @code{upto} and @code{downto} respectively except
-that they are exclusive rather than inclusive limits:
+@table @code
+@item repeat @var{integer}
+This clause simply counts up to the specified number using an
+internal temporary variable. The loops
@example
-(cl-loop for x to 10 collect x)
- @result{} (0 1 2 3 4 5 6 7 8 9 10)
-(cl-loop for x below 10 collect x)
- @result{} (0 1 2 3 4 5 6 7 8 9)
+(cl-loop repeat (1+ n) do @dots{})
+(cl-loop for temp to n do @dots{})
@end example
-The @code{by} value is always positive, even for downward-counting
-loops. Some sort of @code{from} value is required for downward
-loops; @samp{for x downto 5} is not a valid loop clause all by
-itself.
+@noindent
+are identical except that the second one forces you to choose
+a name for a variable you aren't actually going to use.
-@item for @var{var} in @var{list} by @var{function}
-This clause iterates @var{var} over all the elements of @var{list},
-in turn. If you specify the @code{by} term, then @var{function}
-is used to traverse the list instead of @code{cdr}; it must be a
-function taking one argument. For example:
+@item while @var{condition}
+This clause stops the loop when the specified condition (any Lisp
+expression) becomes @code{nil}. For example, the following two
+loops are equivalent, except for the implicit @code{nil} block
+that surrounds the second one:
@example
-(cl-loop for x in '(1 2 3 4 5 6) collect (* x x))
- @result{} (1 4 9 16 25 36)
-(cl-loop for x in '(1 2 3 4 5 6) by 'cddr collect (* x x))
- @result{} (1 9 25)
+(while @var{cond} @var{forms}@dots{})
+(cl-loop while @var{cond} do @var{forms}@dots{})
@end example
-@item for @var{var} on @var{list} by @var{function}
-This clause iterates @var{var} over all the cons cells of @var{list}.
-
-@example
-(cl-loop for x on '(1 2 3 4) collect x)
- @result{} ((1 2 3 4) (2 3 4) (3 4) (4))
-@end example
+@item until @var{condition}
+This clause stops the loop when the specified condition is true,
+i.e., non-@code{nil}.
-With @code{by}, there is no real reason that the @code{on} expression
-must be a list. For example:
+@item always @var{condition}
+This clause stops the loop when the specified condition is @code{nil}.
+Unlike @code{while}, it stops the loop using @code{return nil} so that
+the @code{finally} clauses are not executed. If all the conditions
+were non-@code{nil}, the loop returns @code{t}:
@example
-(cl-loop for x on first-animal by 'next-animal collect x)
+(if (cl-loop for size in size-list always (> size 10))
+ (some-big-sizes)
+ (no-big-sizes))
@end example
-@noindent
-where @code{(next-animal x)} takes an ``animal'' @var{x} and returns
-the next in the (assumed) sequence of animals, or @code{nil} if
-@var{x} was the last animal in the sequence.
+@item never @var{condition}
+This clause is like @code{always}, except that the loop returns
+@code{t} if any conditions were false, or @code{nil} otherwise.
-@item for @var{var} in-ref @var{list} by @var{function}
-This is like a regular @code{in} clause, but @var{var} becomes
-a @code{setf}-able ``reference'' onto the elements of the list
-rather than just a temporary variable. For example,
+@item thereis @var{condition}
+This clause stops the loop when the specified form is non-@code{nil};
+in this case, it returns that non-@code{nil} value. If all the
+values were @code{nil}, the loop returns @code{nil}.
+@end table
-@example
-(cl-loop for x in-ref my-list do (cl-incf x))
-@end example
+@node Accumulation Clauses
+@subsection Accumulation Clauses
@noindent
-increments every element of @code{my-list} in place. This clause
-is an extension to standard Common Lisp.
-
-@item for @var{var} across @var{array}
-This clause iterates @var{var} over all the elements of @var{array},
-which may be a vector or a string.
+These clauses cause the loop to accumulate information about the
+specified Lisp @var{form}. The accumulated result is returned
+from the loop unless overridden, say, by a @code{return} clause.
-@example
-(cl-loop for x across "aeiou"
- do (use-vowel (char-to-string x)))
-@end example
+@table @code
+@item collect @var{form}
+This clause collects the values of @var{form} into a list. Several
+examples of @code{collect} appear elsewhere in this manual.
-@item for @var{var} across-ref @var{array}
-This clause iterates over an array, with @var{var} a @code{setf}-able
-reference onto the elements; see @code{in-ref} above.
+The word @code{collecting} is a synonym for @code{collect}, and
+likewise for the other accumulation clauses.
-@item for @var{var} being the elements of @var{sequence}
-This clause iterates over the elements of @var{sequence}, which may
-be a list, vector, or string. Since the type must be determined
-at run-time, this is somewhat less efficient than @code{in} or
-@code{across}. The clause may be followed by the additional term
-@samp{using (index @var{var2})} to cause @var{var2} to be bound to
-the successive indices (starting at 0) of the elements.
+@item append @var{form}
+This clause collects lists of values into a result list using
+@code{append}.
-This clause type is taken from older versions of the @code{loop} macro,
-and is not present in modern Common Lisp. The @samp{using (sequence ...)}
-term of the older macros is not supported.
+@item nconc @var{form}
+This clause collects lists of values into a result list by
+destructively modifying the lists rather than copying them.
-@item for @var{var} being the elements of-ref @var{sequence}
-This clause iterates over a sequence, with @var{var} a @code{setf}-able
-reference onto the elements; see @code{in-ref} above.
+@item concat @var{form}
+This clause concatenates the values of the specified @var{form}
+into a string. (It and the following clause are extensions to
+standard Common Lisp.)
-@item for @var{var} being the symbols [of @var{obarray}]
-This clause iterates over symbols, either over all interned symbols
-or over all symbols in @var{obarray}. The loop is executed with
-@var{var} bound to each symbol in turn. The symbols are visited in
-an unspecified order.
+@item vconcat @var{form}
+This clause concatenates the values of the specified @var{form}
+into a vector.
-As an example,
+@item count @var{form}
+This clause counts the number of times the specified @var{form}
+evaluates to a non-@code{nil} value.
-@example
-(cl-loop for sym being the symbols
- when (fboundp sym)
- when (string-match "^map" (symbol-name sym))
- collect sym)
-@end example
+@item sum @var{form}
+This clause accumulates the sum of the values of the specified
+@var{form}, which must evaluate to a number.
-@noindent
-returns a list of all the functions whose names begin with @samp{map}.
+@item maximize @var{form}
+This clause accumulates the maximum value of the specified @var{form},
+which must evaluate to a number. The return value is undefined if
+@code{maximize} is executed zero times.
-The Common Lisp words @code{external-symbols} and @code{present-symbols}
-are also recognized but are equivalent to @code{symbols} in Emacs Lisp.
+@item minimize @var{form}
+This clause accumulates the minimum value of the specified @var{form}.
+@end table
-Due to a minor implementation restriction, it will not work to have
-more than one @code{for} clause iterating over symbols, hash tables,
-keymaps, overlays, or intervals in a given @code{cl-loop}. Fortunately,
-it would rarely if ever be useful to do so. It @emph{is} valid to mix
-one of these types of clauses with other clauses like @code{for ... to}
-or @code{while}.
+Accumulation clauses can be followed by @samp{into @var{var}} to
+cause the data to be collected into variable @var{var} (which is
+automatically @code{let}-bound during the loop) rather than an
+unnamed temporary variable. Also, @code{into} accumulations do
+not automatically imply a return value. The loop must use some
+explicit mechanism, such as @code{finally return}, to return
+the accumulated result.
-@item for @var{var} being the hash-keys of @var{hash-table}
-@itemx for @var{var} being the hash-values of @var{hash-table}
-This clause iterates over the entries in @var{hash-table} with
-@var{var} bound to each key, or value. A @samp{using} clause can bind
-a second variable to the opposite part.
+It is valid for several accumulation clauses of the same type to
+accumulate into the same place. From Steele:
@example
-(cl-loop for k being the hash-keys of h
- using (hash-values v)
- do
- (message "key %S -> value %S" k v))
+(cl-loop for name in '(fred sue alice joe june)
+ for kids in '((bob ken) () () (kris sunshine) ())
+ collect name
+ append kids)
+ @result{} (fred bob ken sue alice joe kris sunshine june)
@end example
-@item for @var{var} being the key-codes of @var{keymap}
-@itemx for @var{var} being the key-bindings of @var{keymap}
-This clause iterates over the entries in @var{keymap}.
-The iteration does not enter nested keymaps but does enter inherited
-(parent) keymaps.
-A @code{using} clause can access both the codes and the bindings
-together.
+@node Other Clauses
+@subsection Other Clauses
+
+@noindent
+This section describes the remaining loop clauses.
+
+@table @code
+@item with @var{var} = @var{value}
+This clause binds a variable to a value around the loop, but
+otherwise leaves the variable alone during the loop. The following
+loops are basically equivalent:
@example
-(cl-loop for c being the key-codes of (current-local-map)
- using (key-bindings b)
- do
- (message "key %S -> binding %S" c b))
+(cl-loop with x = 17 do @dots{})
+(let ((x 17)) (cl-loop do @dots{}))
+(cl-loop for x = 17 then x do @dots{})
@end example
+Naturally, the variable @var{var} might be used for some purpose
+in the rest of the loop. For example:
-@item for @var{var} being the key-seqs of @var{keymap}
-This clause iterates over all key sequences defined by @var{keymap}
-and its nested keymaps, where @var{var} takes on values which are
-vectors. The strings or vectors
-are reused for each iteration, so you must copy them if you wish to keep
-them permanently. You can add a @samp{using (key-bindings ...)}
-clause to get the command bindings as well.
-
-@item for @var{var} being the overlays [of @var{buffer}] @dots{}
-This clause iterates over the ``overlays'' of a buffer
-(the clause @code{extents} is synonymous
-with @code{overlays}). If the @code{of} term is omitted, the current
-buffer is used.
-This clause also accepts optional @samp{from @var{pos}} and
-@samp{to @var{pos}} terms, limiting the clause to overlays which
-overlap the specified region.
+@example
+(cl-loop for x in my-list with res = nil do (push x res)
+ finally return res)
+@end example
-@item for @var{var} being the intervals [of @var{buffer}] @dots{}
-This clause iterates over all intervals of a buffer with constant
-text properties. The variable @var{var} will be bound to conses
-of start and end positions, where one start position is always equal
-to the previous end position. The clause allows @code{of},
-@code{from}, @code{to}, and @code{property} terms, where the latter
-term restricts the search to just the specified property. The
-@code{of} term may specify either a buffer or a string.
+This loop inserts the elements of @code{my-list} at the front of
+a new list being accumulated in @code{res}, then returns the
+list @code{res} at the end of the loop. The effect is similar
+to that of a @code{collect} clause, but the list gets reversed
+by virtue of the fact that elements are being pushed onto the
+front of @code{res} rather than the end.
-@item for @var{var} being the frames
-This clause iterates over all Emacs frames. The clause @code{screens} is
-a synonym for @code{frames}. The frames are visited in
-@code{next-frame} order starting from @code{selected-frame}.
+If you omit the @code{=} term, the variable is initialized to
+@code{nil}. (Thus the @samp{= nil} in the above example is
+unnecessary.)
-@item for @var{var} being the windows [of @var{frame}]
-This clause iterates over the windows (in the Emacs sense) of
-the current frame, or of the specified @var{frame}. It visits windows
-in @code{next-window} order starting from @code{selected-window}
-(or @code{frame-selected-window} if you specify @var{frame}).
-This clause treats the minibuffer window in the same way as
-@code{next-window} does. For greater flexibility, consider using
-@code{walk-windows} instead.
+Bindings made by @code{with} are sequential by default, as if
+by @code{let*}. Just like @code{for} clauses, @code{with} clauses
+can be linked with @code{and} to cause the bindings to be made by
+@code{let} instead.
-@item for @var{var} being the buffers
-This clause iterates over all buffers in Emacs. It is equivalent
-to @samp{for @var{var} in (buffer-list)}.
+@item if @var{condition} @var{clause}
+This clause executes the following loop clause only if the specified
+condition is true. The following @var{clause} should be an accumulation,
+@code{do}, @code{return}, @code{if}, or @code{unless} clause.
+Several clauses may be linked by separating them with @code{and}.
+These clauses may be followed by @code{else} and a clause or clauses
+to execute if the condition was false. The whole construct may
+optionally be followed by the word @code{end} (which may be used to
+disambiguate an @code{else} or @code{and} in a nested @code{if}).
-@item for @var{var} = @var{expr1} then @var{expr2}
-This clause does a general iteration. The first time through
-the loop, @var{var} will be bound to @var{expr1}. On the second
-and successive iterations it will be set by evaluating @var{expr2}
-(which may refer to the old value of @var{var}). For example,
-these two loops are effectively the same:
+The actual non-@code{nil} value of the condition form is available
+by the name @code{it} in the ``then'' part. For example:
@example
-(cl-loop for x on my-list by 'cddr do ...)
-(cl-loop for x = my-list then (cddr x) while x do ...)
+(setq funny-numbers '(6 13 -1))
+ @result{} (6 13 -1)
+(cl-loop for x below 10
+ if (cl-oddp x)
+ collect x into odds
+ and if (memq x funny-numbers) return (cdr it) end
+ else
+ collect x into evens
+ finally return (vector odds evens))
+ @result{} [(1 3 5 7 9) (0 2 4 6 8)]
+(setq funny-numbers '(6 7 13 -1))
+ @result{} (6 7 13 -1)
+(cl-loop <@r{same thing again}>)
+ @result{} (13 -1)
@end example
-Note that this type of @code{for} clause does not imply any sort
-of terminating condition; the above example combines it with a
-@code{while} clause to tell when to end the loop.
+Note the use of @code{and} to put two clauses into the ``then''
+part, one of which is itself an @code{if} clause. Note also that
+@code{end}, while normally optional, was necessary here to make
+it clear that the @code{else} refers to the outermost @code{if}
+clause. In the first case, the loop returns a vector of lists
+of the odd and even values of @var{x}. In the second case, the
+odd number 7 is one of the @code{funny-numbers} so the loop
+returns early; the actual returned value is based on the result
+of the @code{memq} call.
-If you omit the @code{then} term, @var{expr1} is used both for
-the initial setting and for successive settings:
+@item when @var{condition} @var{clause}
+This clause is just a synonym for @code{if}.
-@example
-(cl-loop for x = (random) when (> x 0) return x)
-@end example
+@item unless @var{condition} @var{clause}
+The @code{unless} clause is just like @code{if} except that the
+sense of the condition is reversed.
-@noindent
-This loop keeps taking random numbers from the @code{(random)}
-function until it gets a positive one, which it then returns.
-@end table
+@item named @var{name}
+This clause gives a name other than @code{nil} to the implicit
+block surrounding the loop. The @var{name} is the symbol to be
+used as the block name.
-If you include several @code{for} clauses in a row, they are
-treated sequentially (as if by @code{let*} and @code{setq}).
-You can instead use the word @code{and} to link the clauses,
-in which case they are processed in parallel (as if by @code{let}
-and @code{cl-psetq}).
+@item initially [do] @var{forms}@dots{}
+This keyword introduces one or more Lisp forms which will be
+executed before the loop itself begins (but after any variables
+requested by @code{for} or @code{with} have been bound to their
+initial values). @code{initially} clauses can appear anywhere;
+if there are several, they are executed in the order they appear
+in the loop. The keyword @code{do} is optional.
-@example
-(cl-loop for x below 5 for y = nil then x collect (list x y))
- @result{} ((0 nil) (1 1) (2 2) (3 3) (4 4))
-(cl-loop for x below 5 and y = nil then x collect (list x y))
- @result{} ((0 nil) (1 0) (2 1) (3 2) (4 3))
-@end example
+@item finally [do] @var{forms}@dots{}
+This introduces Lisp forms which will be executed after the loop
+finishes (say, on request of a @code{for} or @code{while}).
+@code{initially} and @code{finally} clauses may appear anywhere
+in the loop construct, but they are executed (in the specified
+order) at the beginning or end, respectively, of the loop.
-@noindent
-In the first loop, @code{y} is set based on the value of @code{x}
-that was just set by the previous clause; in the second loop,
-@code{x} and @code{y} are set simultaneously so @code{y} is set
-based on the value of @code{x} left over from the previous time
-through the loop.
+@item finally return @var{form}
+This says that @var{form} should be executed after the loop
+is done to obtain a return value. (Without this, or some other
+clause like @code{collect} or @code{return}, the loop will simply
+return @code{nil}.) Variables bound by @code{for}, @code{with},
+or @code{into} will still contain their final values when @var{form}
+is executed.
-Another feature of the @code{cl-loop} macro is @dfn{destructuring},
-similar in concept to the destructuring provided by @code{defmacro}.
-The @var{var} part of any @code{for} clause can be given as a list
-of variables instead of a single variable. The values produced
-during loop execution must be lists; the values in the lists are
-stored in the corresponding variables.
+@item do @var{forms}@dots{}
+The word @code{do} may be followed by any number of Lisp expressions
+which are executed as an implicit @code{progn} in the body of the
+loop. Many of the examples in this section illustrate the use of
+@code{do}.
-@example
-(cl-loop for (x y) in '((2 3) (4 5) (6 7)) collect (+ x y))
- @result{} (5 9 13)
-@end example
+@item return @var{form}
+This clause causes the loop to return immediately. The following
+Lisp form is evaluated to give the return value of the loop
+form. The @code{finally} clauses, if any, are not executed.
+Of course, @code{return} is generally used inside an @code{if} or
+@code{unless}, as its use in a top-level loop clause would mean
+the loop would never get to ``loop'' more than once.
-In loop destructuring, if there are more values than variables
-the trailing values are ignored, and if there are more variables
-than values the trailing variables get the value @code{nil}.
-If @code{nil} is used as a variable name, the corresponding
-values are ignored. Destructuring may be nested, and dotted
-lists of variables like @code{(x . y)} are allowed, so for example
-to process an alist
+The clause @samp{return @var{form}} is equivalent to
+@samp{do (cl-return @var{form})} (or @code{cl-return-from} if the loop
+was named). The @code{return} clause is implemented a bit more
+efficiently, though.
+@end table
-@example
-(cl-loop for (key . value) in '((a . 1) (b . 2))
- collect value)
- @result{} (1 2)
-@end example
+While there is no high-level way to add user extensions to @code{cl-loop},
+this package does offer two properties called @code{cl-loop-handler}
+and @code{cl-loop-for-handler} which are functions to be called when a
+given symbol is encountered as a top-level loop clause or @code{for}
+clause, respectively. Consult the source code in file
+@file{cl-macs.el} for details.
-@node Iteration Clauses
-@subsection Iteration Clauses
+This package's @code{cl-loop} macro is compatible with that of Common
+Lisp, except that a few features are not implemented: @code{loop-finish}
+and data-type specifiers. Naturally, the @code{for} clauses that
+iterate over keymaps, overlays, intervals, frames, windows, and
+buffers are Emacs-specific extensions.
+
+@node Multiple Values
+@section Multiple Values
@noindent
-Aside from @code{for} clauses, there are several other loop clauses
-that control the way the loop operates. They might be used by
-themselves, or in conjunction with one or more @code{for} clauses.
+Common Lisp functions can return zero or more results. Emacs Lisp
+functions, by contrast, always return exactly one result. This
+package makes no attempt to emulate Common Lisp multiple return
+values; Emacs versions of Common Lisp functions that return more
+than one value either return just the first value (as in
+@code{cl-compiler-macroexpand}) or return a list of values.
+This package @emph{does} define placeholders
+for the Common Lisp functions that work with multiple values, but
+in Emacs Lisp these functions simply operate on lists instead.
+The @code{cl-values} form, for example, is a synonym for @code{list}
+in Emacs.
-@table @code
-@item repeat @var{integer}
-This clause simply counts up to the specified number using an
-internal temporary variable. The loops
+@defmac cl-multiple-value-bind (var@dots{}) values-form forms@dots{}
+This form evaluates @var{values-form}, which must return a list of
+values. It then binds the @var{var}s to these respective values,
+as if by @code{let}, and then executes the body @var{forms}.
+If there are more @var{var}s than values, the extra @var{var}s
+are bound to @code{nil}. If there are fewer @var{var}s than
+values, the excess values are ignored.
+@end defmac
-@example
-(cl-loop repeat (1+ n) do ...)
-(cl-loop for temp to n do ...)
-@end example
+@defmac cl-multiple-value-setq (var@dots{}) form
+This form evaluates @var{form}, which must return a list of values.
+It then sets the @var{var}s to these respective values, as if by
+@code{setq}. Extra @var{var}s or values are treated the same as
+in @code{cl-multiple-value-bind}.
+@end defmac
+
+Since a perfect emulation is not feasible in Emacs Lisp, this
+package opts to keep it as simple and predictable as possible.
+
+@node Macros
+@chapter Macros
@noindent
-are identical except that the second one forces you to choose
-a name for a variable you aren't actually going to use.
+This package implements the various Common Lisp features of
+@code{defmacro}, such as destructuring, @code{&environment},
+and @code{&body}. Top-level @code{&whole} is not implemented
+for @code{defmacro} due to technical difficulties.
+@xref{Argument Lists}.
-@item while @var{condition}
-This clause stops the loop when the specified condition (any Lisp
-expression) becomes @code{nil}. For example, the following two
-loops are equivalent, except for the implicit @code{nil} block
-that surrounds the second one:
+Destructuring is made available to the user by way of the
+following macro:
-@example
-(while @var{cond} @var{forms}@dots{})
-(cl-loop while @var{cond} do @var{forms}@dots{})
-@end example
+@defmac cl-destructuring-bind arglist expr forms@dots{}
+This macro expands to code that executes @var{forms}, with
+the variables in @var{arglist} bound to the list of values
+returned by @var{expr}. The @var{arglist} can include all
+the features allowed for @code{cl-defmacro} argument lists,
+including destructuring. (The @code{&environment} keyword
+is not allowed.) The macro expansion will signal an error
+if @var{expr} returns a list of the wrong number of arguments
+or with incorrect keyword arguments.
+@end defmac
-@item until @var{condition}
-This clause stops the loop when the specified condition is true,
-i.e., non-@code{nil}.
+This package also includes the Common Lisp @code{define-compiler-macro}
+facility, which allows you to define compile-time expansions and
+optimizations for your functions.
-@item always @var{condition}
-This clause stops the loop when the specified condition is @code{nil}.
-Unlike @code{while}, it stops the loop using @code{return nil} so that
-the @code{finally} clauses are not executed. If all the conditions
-were non-@code{nil}, the loop returns @code{t}:
+@defmac cl-define-compiler-macro name arglist forms@dots{}
+This form is similar to @code{defmacro}, except that it only expands
+calls to @var{name} at compile-time; calls processed by the Lisp
+interpreter are not expanded, nor are they expanded by the
+@code{macroexpand} function.
+
+The argument list may begin with a @code{&whole} keyword and a
+variable. This variable is bound to the macro-call form itself,
+i.e., to a list of the form @samp{(@var{name} @var{args}@dots{})}.
+If the macro expander returns this form unchanged, then the
+compiler treats it as a normal function call. This allows
+compiler macros to work as optimizers for special cases of a
+function, leaving complicated cases alone.
+
+For example, here is a simplified version of a definition that
+appears as a standard part of this package:
@example
-(if (cl-loop for size in size-list always (> size 10))
- (some-big-sizes)
- (no-big-sizes))
+(cl-define-compiler-macro cl-member (&whole form a list &rest keys)
+ (if (and (null keys)
+ (eq (car-safe a) 'quote)
+ (not (floatp (cadr a))))
+ (list 'memq a list)
+ form))
@end example
-@item never @var{condition}
-This clause is like @code{always}, except that the loop returns
-@code{t} if any conditions were false, or @code{nil} otherwise.
+@noindent
+This definition causes @code{(cl-member @var{a} @var{list})} to change
+to a call to the faster @code{memq} in the common case where @var{a}
+is a non-floating-point constant; if @var{a} is anything else, or
+if there are any keyword arguments in the call, then the original
+@code{cl-member} call is left intact. (The actual compiler macro
+for @code{cl-member} optimizes a number of other cases, including
+common @code{:test} predicates.)
+@end defmac
-@item thereis @var{condition}
-This clause stops the loop when the specified form is non-@code{nil};
-in this case, it returns that non-@code{nil} value. If all the
-values were @code{nil}, the loop returns @code{nil}.
-@end table
+@defun cl-compiler-macroexpand form
+This function is analogous to @code{macroexpand}, except that it
+expands compiler macros rather than regular macros. It returns
+@var{form} unchanged if it is not a call to a function for which
+a compiler macro has been defined, or if that compiler macro
+decided to punt by returning its @code{&whole} argument. Like
+@code{macroexpand}, it expands repeatedly until it reaches a form
+for which no further expansion is possible.
+@end defun
-@node Accumulation Clauses
-@subsection Accumulation Clauses
+@xref{Macro Bindings}, for descriptions of the @code{cl-macrolet}
+and @code{cl-symbol-macrolet} forms for making ``local'' macro
+definitions.
+
+@node Declarations
+@chapter Declarations
@noindent
-These clauses cause the loop to accumulate information about the
-specified Lisp @var{form}. The accumulated result is returned
-from the loop unless overridden, say, by a @code{return} clause.
+Common Lisp includes a complex and powerful ``declaration''
+mechanism that allows you to give the compiler special hints
+about the types of data that will be stored in particular variables,
+and about the ways those variables and functions will be used. This
+package defines versions of all the Common Lisp declaration forms:
+@code{declare}, @code{locally}, @code{proclaim}, @code{declaim},
+and @code{the}.
-@table @code
-@item collect @var{form}
-This clause collects the values of @var{form} into a list. Several
-examples of @code{collect} appear elsewhere in this manual.
+Most of the Common Lisp declarations are not currently useful in Emacs
+Lisp. For example, the byte-code system provides little
+opportunity to benefit from type information.
+@ignore
+and @code{special} declarations are redundant in a fully
+dynamically-scoped Lisp.
+@end ignore
+A few declarations are meaningful when byte compiler optimizations
+are enabled, as they are by the default. Otherwise these
+declarations will effectively be ignored.
-The word @code{collecting} is a synonym for @code{collect}, and
-likewise for the other accumulation clauses.
+@defun cl-proclaim decl-spec
+This function records a ``global'' declaration specified by
+@var{decl-spec}. Since @code{cl-proclaim} is a function, @var{decl-spec}
+is evaluated and thus should normally be quoted.
+@end defun
-@item append @var{form}
-This clause collects lists of values into a result list using
-@code{append}.
+@defmac cl-declaim decl-specs@dots{}
+This macro is like @code{cl-proclaim}, except that it takes any number
+of @var{decl-spec} arguments, and the arguments are unevaluated and
+unquoted. The @code{cl-declaim} macro also puts @code{(cl-eval-when
+(compile load eval) @dots{})} around the declarations so that they will
+be registered at compile-time as well as at run-time. (This is vital,
+since normally the declarations are meant to influence the way the
+compiler treats the rest of the file that contains the @code{cl-declaim}
+form.)
+@end defmac
-@item nconc @var{form}
-This clause collects lists of values into a result list by
-destructively modifying the lists rather than copying them.
+@defmac cl-declare decl-specs@dots{}
+This macro is used to make declarations within functions and other
+code. Common Lisp allows declarations in various locations, generally
+at the beginning of any of the many ``implicit @code{progn}s''
+throughout Lisp syntax, such as function bodies, @code{let} bodies,
+etc. Currently the only declaration understood by @code{cl-declare}
+is @code{special}.
+@end defmac
-@item concat @var{form}
-This clause concatenates the values of the specified @var{form}
-into a string. (It and the following clause are extensions to
-standard Common Lisp.)
+@defmac cl-locally declarations@dots{} forms@dots{}
+In this package, @code{cl-locally} is no different from @code{progn}.
+@end defmac
-@item vconcat @var{form}
-This clause concatenates the values of the specified @var{form}
-into a vector.
+@defmac cl-the type form
+Type information provided by @code{cl-the} is ignored in this package;
+in other words, @code{(cl-the @var{type} @var{form})} is equivalent to
+@var{form}. Future byte-compiler optimizations may make use of this
+information.
-@item count @var{form}
-This clause counts the number of times the specified @var{form}
-evaluates to a non-@code{nil} value.
+For example, @code{mapcar} can map over both lists and arrays. It is
+hard for the compiler to expand @code{mapcar} into an in-line loop
+unless it knows whether the sequence will be a list or an array ahead
+of time. With @code{(mapcar 'car (cl-the vector foo))}, a future
+compiler would have enough information to expand the loop in-line.
+For now, Emacs Lisp will treat the above code as exactly equivalent
+to @code{(mapcar 'car foo)}.
+@end defmac
-@item sum @var{form}
-This clause accumulates the sum of the values of the specified
-@var{form}, which must evaluate to a number.
+Each @var{decl-spec} in a @code{cl-proclaim}, @code{cl-declaim}, or
+@code{cl-declare} should be a list beginning with a symbol that says
+what kind of declaration it is. This package currently understands
+@code{special}, @code{inline}, @code{notinline}, @code{optimize},
+and @code{warn} declarations. (The @code{warn} declaration is an
+extension of standard Common Lisp.) Other Common Lisp declarations,
+such as @code{type} and @code{ftype}, are silently ignored.
-@item maximize @var{form}
-This clause accumulates the maximum value of the specified @var{form},
-which must evaluate to a number. The return value is undefined if
-@code{maximize} is executed zero times.
+@table @code
+@item special
+@c FIXME ?
+Since all variables in Emacs Lisp are ``special'' (in the Common
+Lisp sense), @code{special} declarations are only advisory. They
+simply tell the byte compiler that the specified
+variables are intentionally being referred to without being
+bound in the body of the function. The compiler normally emits
+warnings for such references, since they could be typographical
+errors for references to local variables.
-@item minimize @var{form}
-This clause accumulates the minimum value of the specified @var{form}.
-@end table
+The declaration @code{(cl-declare (special @var{var1} @var{var2}))} is
+equivalent to @code{(defvar @var{var1}) (defvar @var{var2})}.
-Accumulation clauses can be followed by @samp{into @var{var}} to
-cause the data to be collected into variable @var{var} (which is
-automatically @code{let}-bound during the loop) rather than an
-unnamed temporary variable. Also, @code{into} accumulations do
-not automatically imply a return value. The loop must use some
-explicit mechanism, such as @code{finally return}, to return
-the accumulated result.
+In top-level contexts, it is generally better to write
+@code{(defvar @var{var})} than @code{(cl-declaim (special @var{var}))},
+since @code{defvar} makes your intentions clearer.
-It is valid for several accumulation clauses of the same type to
-accumulate into the same place. From Steele:
+@item inline
+The @code{inline} @var{decl-spec} lists one or more functions
+whose bodies should be expanded ``in-line'' into calling functions
+whenever the compiler is able to arrange for it. For example,
+the function @code{cl-acons} is declared @code{inline}
+by this package so that the form @code{(cl-acons @var{key} @var{value}
+@var{alist})} will
+expand directly into @code{(cons (cons @var{key} @var{value}) @var{alist})}
+when it is called in user functions, so as to save function calls.
+
+The following declarations are all equivalent. Note that the
+@code{defsubst} form is a convenient way to define a function
+and declare it inline all at once.
@example
-(cl-loop for name in '(fred sue alice joe june)
- for kids in '((bob ken) () () (kris sunshine) ())
- collect name
- append kids)
- @result{} (fred bob ken sue alice joe kris sunshine june)
+(cl-declaim (inline foo bar))
+(cl-eval-when (compile load eval)
+ (cl-proclaim '(inline foo bar)))
+(defsubst foo (@dots{}) @dots{}) ; instead of defun
@end example
-@node Other Clauses
-@subsection Other Clauses
+@strong{Please note:} this declaration remains in effect after the
+containing source file is done. It is correct to use it to
+request that a function you have defined should be inlined,
+but it is impolite to use it to request inlining of an external
+function.
-@noindent
-This section describes the remaining loop clauses.
+In Common Lisp, it is possible to use @code{(declare (inline @dots{}))}
+before a particular call to a function to cause just that call to
+be inlined; the current byte compilers provide no way to implement
+this, so @code{(cl-declare (inline @dots{}))} is currently ignored by
+this package.
-@table @code
-@item with @var{var} = @var{value}
-This clause binds a variable to a value around the loop, but
-otherwise leaves the variable alone during the loop. The following
-loops are basically equivalent:
+@item notinline
+The @code{notinline} declaration lists functions which should
+not be inlined after all; it cancels a previous @code{inline}
+declaration.
-@example
-(cl-loop with x = 17 do ...)
-(let ((x 17)) (cl-loop do ...))
-(cl-loop for x = 17 then x do ...)
-@end example
+@item optimize
+This declaration controls how much optimization is performed by
+the compiler.
-Naturally, the variable @var{var} might be used for some purpose
-in the rest of the loop. For example:
+The word @code{optimize} is followed by any number of lists like
+@code{(speed 3)} or @code{(safety 2)}. Common Lisp defines several
+optimization ``qualities''; this package ignores all but @code{speed}
+and @code{safety}. The value of a quality should be an integer from
+0 to 3, with 0 meaning ``unimportant'' and 3 meaning ``very important''.
+The default level for both qualities is 1.
-@example
-(cl-loop for x in my-list with res = nil do (push x res)
- finally return res)
-@end example
+In this package, the @code{speed} quality is tied to the @code{byte-optimize}
+flag, which is set to @code{nil} for @code{(speed 0)} and to
+@code{t} for higher settings; and the @code{safety} quality is
+tied to the @code{byte-compile-delete-errors} flag, which is
+set to @code{nil} for @code{(safety 3)} and to @code{t} for all
+lower settings. (The latter flag controls whether the compiler
+is allowed to optimize out code whose only side-effect could
+be to signal an error, e.g., rewriting @code{(progn foo bar)} to
+@code{bar} when it is not known whether @code{foo} will be bound
+at run-time.)
-This loop inserts the elements of @code{my-list} at the front of
-a new list being accumulated in @code{res}, then returns the
-list @code{res} at the end of the loop. The effect is similar
-to that of a @code{collect} clause, but the list gets reversed
-by virtue of the fact that elements are being pushed onto the
-front of @code{res} rather than the end.
+Note that even compiling with @code{(safety 0)}, the Emacs
+byte-code system provides sufficient checking to prevent real
+harm from being done. For example, barring serious bugs in
+Emacs itself, Emacs will not crash with a segmentation fault
+just because of an error in a fully-optimized Lisp program.
-If you omit the @code{=} term, the variable is initialized to
-@code{nil}. (Thus the @samp{= nil} in the above example is
-unnecessary.)
+The @code{optimize} declaration is normally used in a top-level
+@code{cl-proclaim} or @code{cl-declaim} in a file; Common Lisp allows
+it to be used with @code{declare} to set the level of optimization
+locally for a given form, but this will not work correctly with the
+current byte-compiler. (The @code{cl-declare}
+will set the new optimization level, but that level will not
+automatically be unset after the enclosing form is done.)
-Bindings made by @code{with} are sequential by default, as if
-by @code{let*}. Just like @code{for} clauses, @code{with} clauses
-can be linked with @code{and} to cause the bindings to be made by
-@code{let} instead.
+@item warn
+This declaration controls what sorts of warnings are generated
+by the byte compiler. The word @code{warn} is followed by any
+number of ``warning qualities'', similar in form to optimization
+qualities. The currently supported warning types are
+@code{redefine}, @code{callargs}, @code{unresolved}, and
+@code{free-vars}; in the current system, a value of 0 will
+disable these warnings and any higher value will enable them.
+See the documentation of the variable @code{byte-compile-warnings}
+for more details.
+@end table
-@item if @var{condition} @var{clause}
-This clause executes the following loop clause only if the specified
-condition is true. The following @var{clause} should be an accumulation,
-@code{do}, @code{return}, @code{if}, or @code{unless} clause.
-Several clauses may be linked by separating them with @code{and}.
-These clauses may be followed by @code{else} and a clause or clauses
-to execute if the condition was false. The whole construct may
-optionally be followed by the word @code{end} (which may be used to
-disambiguate an @code{else} or @code{and} in a nested @code{if}).
+@node Symbols
+@chapter Symbols
-The actual non-@code{nil} value of the condition form is available
-by the name @code{it} in the ``then'' part. For example:
+@noindent
+This package defines several symbol-related features that were
+missing from Emacs Lisp.
-@example
-(setq funny-numbers '(6 13 -1))
- @result{} (6 13 -1)
-(cl-loop for x below 10
- if (oddp x)
- collect x into odds
- and if (memq x funny-numbers) return (cdr it) end
- else
- collect x into evens
- finally return (vector odds evens))
- @result{} [(1 3 5 7 9) (0 2 4 6 8)]
-(setq funny-numbers '(6 7 13 -1))
- @result{} (6 7 13 -1)
-(cl-loop <@r{same thing again}>)
- @result{} (13 -1)
-@end example
+@menu
+* Property Lists:: @code{cl-get}, @code{cl-remprop}, @code{cl-getf}, @code{cl-remf}.
+* Creating Symbols:: @code{cl-gensym}, @code{cl-gentemp}.
+@end menu
-Note the use of @code{and} to put two clauses into the ``then''
-part, one of which is itself an @code{if} clause. Note also that
-@code{end}, while normally optional, was necessary here to make
-it clear that the @code{else} refers to the outermost @code{if}
-clause. In the first case, the loop returns a vector of lists
-of the odd and even values of @var{x}. In the second case, the
-odd number 7 is one of the @code{funny-numbers} so the loop
-returns early; the actual returned value is based on the result
-of the @code{memq} call.
+@node Property Lists
+@section Property Lists
-@item when @var{condition} @var{clause}
-This clause is just a synonym for @code{if}.
+@noindent
+These functions augment the standard Emacs Lisp functions @code{get}
+and @code{put} for operating on properties attached to symbols.
+There are also functions for working with property lists as
+first-class data structures not attached to particular symbols.
-@item unless @var{condition} @var{clause}
-The @code{unless} clause is just like @code{if} except that the
-sense of the condition is reversed.
+@defun cl-get symbol property &optional default
+This function is like @code{get}, except that if the property is
+not found, the @var{default} argument provides the return value.
+(The Emacs Lisp @code{get} function always uses @code{nil} as
+the default; this package's @code{cl-get} is equivalent to Common
+Lisp's @code{get}.)
-@item named @var{name}
-This clause gives a name other than @code{nil} to the implicit
-block surrounding the loop. The @var{name} is the symbol to be
-used as the block name.
+The @code{cl-get} function is @code{setf}-able; when used in this
+fashion, the @var{default} argument is allowed but ignored.
+@end defun
-@item initially [do] @var{forms}...
-This keyword introduces one or more Lisp forms which will be
-executed before the loop itself begins (but after any variables
-requested by @code{for} or @code{with} have been bound to their
-initial values). @code{initially} clauses can appear anywhere;
-if there are several, they are executed in the order they appear
-in the loop. The keyword @code{do} is optional.
+@defun cl-remprop symbol property
+This function removes the entry for @var{property} from the property
+list of @var{symbol}. It returns a true value if the property was
+indeed found and removed, or @code{nil} if there was no such property.
+(This function was probably omitted from Emacs originally because,
+since @code{get} did not allow a @var{default}, it was very difficult
+to distinguish between a missing property and a property whose value
+was @code{nil}; thus, setting a property to @code{nil} was close
+enough to @code{cl-remprop} for most purposes.)
+@end defun
-@item finally [do] @var{forms}...
-This introduces Lisp forms which will be executed after the loop
-finishes (say, on request of a @code{for} or @code{while}).
-@code{initially} and @code{finally} clauses may appear anywhere
-in the loop construct, but they are executed (in the specified
-order) at the beginning or end, respectively, of the loop.
+@defun cl-getf place property &optional default
+This function scans the list @var{place} as if it were a property
+list, i.e., a list of alternating property names and values. If
+an even-numbered element of @var{place} is found which is @code{eq}
+to @var{property}, the following odd-numbered element is returned.
+Otherwise, @var{default} is returned (or @code{nil} if no default
+is given).
-@item finally return @var{form}
-This says that @var{form} should be executed after the loop
-is done to obtain a return value. (Without this, or some other
-clause like @code{collect} or @code{return}, the loop will simply
-return @code{nil}.) Variables bound by @code{for}, @code{with},
-or @code{into} will still contain their final values when @var{form}
-is executed.
+In particular,
-@item do @var{forms}...
-The word @code{do} may be followed by any number of Lisp expressions
-which are executed as an implicit @code{progn} in the body of the
-loop. Many of the examples in this section illustrate the use of
-@code{do}.
+@example
+(get sym prop) @equiv{} (cl-getf (symbol-plist sym) prop)
+@end example
-@item return @var{form}
-This clause causes the loop to return immediately. The following
-Lisp form is evaluated to give the return value of the @code{loop}
-form. The @code{finally} clauses, if any, are not executed.
-Of course, @code{return} is generally used inside an @code{if} or
-@code{unless}, as its use in a top-level loop clause would mean
-the loop would never get to ``loop'' more than once.
-
-The clause @samp{return @var{form}} is equivalent to
-@c FIXME cl-do, cl-return?
-@samp{do (return @var{form})} (or @code{return-from} if the loop
-was named). The @code{return} clause is implemented a bit more
-efficiently, though.
-@end table
-
-While there is no high-level way to add user extensions to @code{cl-loop}
-(comparable to @code{defsetf} for @code{setf}, say), this package
-does offer two properties called @code{cl-loop-handler} and
-@code{cl-loop-for-handler} which are functions to be called when
-a given symbol is encountered as a top-level loop clause or
-@code{for} clause, respectively. Consult the source code in
-file @file{cl-macs.el} for details.
+It is valid to use @code{cl-getf} as a @code{setf} place, in which case
+its @var{place} argument must itself be a valid @code{setf} place.
+The @var{default} argument, if any, is ignored in this context.
+The effect is to change (via @code{setcar}) the value cell in the
+list that corresponds to @var{property}, or to cons a new property-value
+pair onto the list if the property is not yet present.
-This package's @code{cl-loop} macro is compatible with that of Common
-Lisp, except that a few features are not implemented: @code{loop-finish}
-and data-type specifiers. Naturally, the @code{for} clauses which
-iterate over keymaps, overlays, intervals, frames, windows, and
-buffers are Emacs-specific extensions.
+@example
+(put sym prop val) @equiv{} (setf (cl-getf (symbol-plist sym) prop) val)
+@end example
-@node Multiple Values
-@section Multiple Values
+The @code{get} and @code{cl-get} functions are also @code{setf}-able.
+The fact that @code{default} is ignored can sometimes be useful:
-@noindent
-Common Lisp functions can return zero or more results. Emacs Lisp
-functions, by contrast, always return exactly one result. This
-package makes no attempt to emulate Common Lisp multiple return
-values; Emacs versions of Common Lisp functions that return more
-than one value either return just the first value (as in
-@code{cl-compiler-macroexpand}) or return a list of values (as in
-@code{get-setf-method}). This package @emph{does} define placeholders
-for the Common Lisp functions that work with multiple values, but
-in Emacs Lisp these functions simply operate on lists instead.
-The @code{values} form, for example, is a synonym for @code{list}
-in Emacs.
+@example
+(cl-incf (cl-get 'foo 'usage-count 0))
+@end example
-@defspec cl-multiple-value-bind (var@dots{}) values-form forms@dots{}
-This form evaluates @var{values-form}, which must return a list of
-values. It then binds the @var{var}s to these respective values,
-as if by @code{let}, and then executes the body @var{forms}.
-If there are more @var{var}s than values, the extra @var{var}s
-are bound to @code{nil}. If there are fewer @var{var}s than
-values, the excess values are ignored.
-@end defspec
+Here, symbol @code{foo}'s @code{usage-count} property is incremented
+if it exists, or set to 1 (an incremented 0) otherwise.
-@defspec cl-multiple-value-setq (var@dots{}) form
-This form evaluates @var{form}, which must return a list of values.
-It then sets the @var{var}s to these respective values, as if by
-@code{setq}. Extra @var{var}s or values are treated the same as
-in @code{cl-multiple-value-bind}.
-@end defspec
+When not used as a @code{setf} form, @code{cl-getf} is just a regular
+function and its @var{place} argument can actually be any Lisp
+expression.
+@end defun
-Since a perfect emulation is not feasible in Emacs Lisp, this
-package opts to keep it as simple and predictable as possible.
+@defmac cl-remf place property
+This macro removes the property-value pair for @var{property} from
+the property list stored at @var{place}, which is any @code{setf}-able
+place expression. It returns true if the property was found. Note
+that if @var{property} happens to be first on the list, this will
+effectively do a @code{(setf @var{place} (cddr @var{place}))},
+whereas if it occurs later, this simply uses @code{setcdr} to splice
+out the property and value cells.
+@end defmac
-@node Macros
-@chapter Macros
+@node Creating Symbols
+@section Creating Symbols
@noindent
-This package implements the various Common Lisp features of
-@code{defmacro}, such as destructuring, @code{&environment},
-and @code{&body}. Top-level @code{&whole} is not implemented
-for @code{defmacro} due to technical difficulties.
-@xref{Argument Lists}.
-
-Destructuring is made available to the user by way of the
-following macro:
-
-@defspec cl-destructuring-bind arglist expr forms@dots{}
-This macro expands to code which executes @var{forms}, with
-the variables in @var{arglist} bound to the list of values
-returned by @var{expr}. The @var{arglist} can include all
-the features allowed for @code{defmacro} argument lists,
-including destructuring. (The @code{&environment} keyword
-is not allowed.) The macro expansion will signal an error
-if @var{expr} returns a list of the wrong number of arguments
-or with incorrect keyword arguments.
-@end defspec
+These functions create unique symbols, typically for use as
+temporary variables.
-This package also includes the Common Lisp @code{cl-define-compiler-macro}
-facility, which allows you to define compile-time expansions and
-optimizations for your functions.
+@defun cl-gensym &optional x
+This function creates a new, uninterned symbol (using @code{make-symbol})
+with a unique name. (The name of an uninterned symbol is relevant
+only if the symbol is printed.) By default, the name is generated
+from an increasing sequence of numbers, @samp{G1000}, @samp{G1001},
+@samp{G1002}, etc. If the optional argument @var{x} is a string, that
+string is used as a prefix instead of @samp{G}. Uninterned symbols
+are used in macro expansions for temporary variables, to ensure that
+their names will not conflict with ``real'' variables in the user's
+code.
-@defspec cl-define-compiler-macro name arglist forms@dots{}
-This form is similar to @code{defmacro}, except that it only expands
-calls to @var{name} at compile-time; calls processed by the Lisp
-interpreter are not expanded, nor are they expanded by the
-@code{macroexpand} function.
+(Internally, the variable @code{cl--gensym-counter} holds the counter
+used to generate names. It is incremented after each use. In Common
+Lisp this is initialized with 0, but this package initializes it with
+a random time-dependent value to avoid trouble when two files that
+each used @code{cl-gensym} in their compilation are loaded together.
+Uninterned symbols become interned when the compiler writes them out
+to a file and the Emacs loader loads them, so their names have to be
+treated a bit more carefully than in Common Lisp where uninterned
+symbols remain uninterned after loading.)
+@end defun
-The argument list may begin with a @code{&whole} keyword and a
-variable. This variable is bound to the macro-call form itself,
-i.e., to a list of the form @samp{(@var{name} @var{args}@dots{})}.
-If the macro expander returns this form unchanged, then the
-compiler treats it as a normal function call. This allows
-compiler macros to work as optimizers for special cases of a
-function, leaving complicated cases alone.
+@defun cl-gentemp &optional x
+This function is like @code{cl-gensym}, except that it produces a new
+@emph{interned} symbol. If the symbol that is generated already
+exists, the function keeps incrementing the counter and trying
+again until a new symbol is generated.
+@end defun
-For example, here is a simplified version of a definition that
-appears as a standard part of this package:
+This package automatically creates all keywords that are called for by
+@code{&key} argument specifiers, and discourages the use of keywords
+as data unrelated to keyword arguments, so the related function
+@code{defkeyword} (to create self-quoting keyword symbols) is not
+provided.
-@example
-(cl-define-compiler-macro cl-member (&whole form a list &rest keys)
- (if (and (null keys)
- (eq (car-safe a) 'quote)
- (not (floatp-safe (cadr a))))
- (list 'memq a list)
- form))
-@end example
+@node Numbers
+@chapter Numbers
@noindent
-This definition causes @code{(cl-member @var{a} @var{list})} to change
-to a call to the faster @code{memq} in the common case where @var{a}
-is a non-floating-point constant; if @var{a} is anything else, or
-if there are any keyword arguments in the call, then the original
-@code{cl-member} call is left intact. (The actual compiler macro
-for @code{cl-member} optimizes a number of other cases, including
-common @code{:test} predicates.)
-@end defspec
-
-@defun cl-compiler-macroexpand form
-This function is analogous to @code{macroexpand}, except that it
-expands compiler macros rather than regular macros. It returns
-@var{form} unchanged if it is not a call to a function for which
-a compiler macro has been defined, or if that compiler macro
-decided to punt by returning its @code{&whole} argument. Like
-@code{macroexpand}, it expands repeatedly until it reaches a form
-for which no further expansion is possible.
-@end defun
+This section defines a few simple Common Lisp operations on numbers
+that were left out of Emacs Lisp.
-@xref{Macro Bindings}, for descriptions of the @code{cl-macrolet}
-and @code{cl-symbol-macrolet} forms for making ``local'' macro
-definitions.
+@menu
+* Predicates on Numbers:: @code{cl-plusp}, @code{cl-oddp}, etc.
+* Numerical Functions:: @code{cl-floor}, @code{cl-ceiling}, etc.
+* Random Numbers:: @code{cl-random}, @code{cl-make-random-state}.
+* Implementation Parameters:: @code{cl-most-positive-float}, etc.
+@end menu
-@node Declarations
-@chapter Declarations
+@node Predicates on Numbers
+@section Predicates on Numbers
@noindent
-Common Lisp includes a complex and powerful ``declaration''
-mechanism that allows you to give the compiler special hints
-about the types of data that will be stored in particular variables,
-and about the ways those variables and functions will be used. This
-package defines versions of all the Common Lisp declaration forms:
-@code{cl-declare}, @code{cl-locally}, @code{cl-proclaim}, @code{cl-declaim},
-and @code{cl-the}.
+These functions return @code{t} if the specified condition is
+true of the numerical argument, or @code{nil} otherwise.
-Most of the Common Lisp declarations are not currently useful in
-Emacs Lisp, as the byte-code system provides little opportunity
-to benefit from type information, and @code{special} declarations
-are redundant in a fully dynamically-scoped Lisp. A few
-declarations are meaningful when the optimizing byte
-compiler is being used, however. Under the earlier non-optimizing
-compiler, these declarations will effectively be ignored.
+@defun cl-plusp number
+This predicate tests whether @var{number} is positive. It is an
+error if the argument is not a number.
+@end defun
-@defun cl-proclaim decl-spec
-This function records a ``global'' declaration specified by
-@var{decl-spec}. Since @code{cl-proclaim} is a function, @var{decl-spec}
-is evaluated and thus should normally be quoted.
+@defun cl-minusp number
+This predicate tests whether @var{number} is negative. It is an
+error if the argument is not a number.
@end defun
-@defspec cl-declaim decl-specs@dots{}
-This macro is like @code{cl-proclaim}, except that it takes any number
-of @var{decl-spec} arguments, and the arguments are unevaluated and
-unquoted. The @code{cl-declaim} macro also puts an @code{(cl-eval-when
-(compile load eval) ...)} around the declarations so that they will
-be registered at compile-time as well as at run-time. (This is vital,
-since normally the declarations are meant to influence the way the
-compiler treats the rest of the file that contains the @code{cl-declaim}
-form.)
-@end defspec
+@defun cl-oddp integer
+This predicate tests whether @var{integer} is odd. It is an
+error if the argument is not an integer.
+@end defun
-@defspec cl-declare decl-specs@dots{}
-This macro is used to make declarations within functions and other
-code. Common Lisp allows declarations in various locations, generally
-at the beginning of any of the many ``implicit @code{progn}s''
-throughout Lisp syntax, such as function bodies, @code{let} bodies,
-etc. Currently the only declaration understood by @code{cl-declare}
-is @code{special}.
-@end defspec
+@defun cl-evenp integer
+This predicate tests whether @var{integer} is even. It is an
+error if the argument is not an integer.
+@end defun
-@defspec cl-locally declarations@dots{} forms@dots{}
-In this package, @code{cl-locally} is no different from @code{progn}.
-@end defspec
+@ignore
+@defun cl-floatp-safe object
+This predicate tests whether @var{object} is a floating-point
+number. On systems that support floating-point, this is equivalent
+to @code{floatp}. On other systems, this always returns @code{nil}.
+@end defun
+@end ignore
-@defspec cl-the type form
-Type information provided by @code{cl-the} is ignored in this package;
-in other words, @code{(cl-the @var{type} @var{form})} is equivalent
-to @var{form}. Future versions of the optimizing byte-compiler may
-make use of this information.
+@node Numerical Functions
+@section Numerical Functions
-For example, @code{mapcar} can map over both lists and arrays. It is
-hard for the compiler to expand @code{mapcar} into an in-line loop
-unless it knows whether the sequence will be a list or an array ahead
-of time. With @code{(mapcar 'car (cl-the vector foo))}, a future
-compiler would have enough information to expand the loop in-line.
-For now, Emacs Lisp will treat the above code as exactly equivalent
-to @code{(mapcar 'car foo)}.
-@end defspec
+@noindent
+These functions perform various arithmetic operations on numbers.
-Each @var{decl-spec} in a @code{cl-proclaim}, @code{cl-declaim}, or
-@code{cl-declare} should be a list beginning with a symbol that says
-what kind of declaration it is. This package currently understands
-@code{special}, @code{inline}, @code{notinline}, @code{optimize},
-and @code{warn} declarations. (The @code{warn} declaration is an
-extension of standard Common Lisp.) Other Common Lisp declarations,
-such as @code{type} and @code{ftype}, are silently ignored.
+@defun cl-gcd &rest integers
+This function returns the Greatest Common Divisor of the arguments.
+For one argument, it returns the absolute value of that argument.
+For zero arguments, it returns zero.
+@end defun
-@table @code
-@item special
-Since all variables in Emacs Lisp are ``special'' (in the Common
-Lisp sense), @code{special} declarations are only advisory. They
-simply tell the optimizing byte compiler that the specified
-variables are intentionally being referred to without being
-bound in the body of the function. The compiler normally emits
-warnings for such references, since they could be typographical
-errors for references to local variables.
+@defun cl-lcm &rest integers
+This function returns the Least Common Multiple of the arguments.
+For one argument, it returns the absolute value of that argument.
+For zero arguments, it returns one.
+@end defun
-The declaration @code{(cl-declare (special @var{var1} @var{var2}))} is
-equivalent to @code{(defvar @var{var1}) (defvar @var{var2})} in the
-optimizing compiler, or to nothing at all in older compilers (which
-do not warn for non-local references).
+@defun cl-isqrt integer
+This function computes the ``integer square root'' of its integer
+argument, i.e., the greatest integer less than or equal to the true
+square root of the argument.
+@end defun
-In top-level contexts, it is generally better to write
-@code{(defvar @var{var})} than @code{(cl-declaim (special @var{var}))},
-since @code{defvar} makes your intentions clearer. But the older
-byte compilers can not handle @code{defvar}s appearing inside of
-functions, while @code{(cl-declare (special @var{var}))} takes care
-to work correctly with all compilers.
+@defun cl-floor number &optional divisor
+With one argument, @code{cl-floor} returns a list of two numbers:
+The argument rounded down (toward minus infinity) to an integer,
+and the ``remainder'' which would have to be added back to the
+first return value to yield the argument again. If the argument
+is an integer @var{x}, the result is always the list @code{(@var{x} 0)}.
+If the argument is a floating-point number, the first
+result is a Lisp integer and the second is a Lisp float between
+0 (inclusive) and 1 (exclusive).
-@item inline
-The @code{inline} @var{decl-spec} lists one or more functions
-whose bodies should be expanded ``in-line'' into calling functions
-whenever the compiler is able to arrange for it. For example,
-the Common Lisp function @code{cadr} is declared @code{inline}
-by this package so that the form @code{(cadr @var{x})} will
-expand directly into @code{(car (cdr @var{x}))} when it is called
-in user functions, for a savings of one (relatively expensive)
-function call.
-
-The following declarations are all equivalent. Note that the
-@code{defsubst} form is a convenient way to define a function
-and declare it inline all at once.
+With two arguments, @code{cl-floor} divides @var{number} by
+@var{divisor}, and returns the floor of the quotient and the
+corresponding remainder as a list of two numbers. If
+@code{(cl-floor @var{x} @var{y})} returns @code{(@var{q} @var{r})},
+then @code{@var{q}*@var{y} + @var{r} = @var{x}}, with @var{r}
+between 0 (inclusive) and @var{r} (exclusive). Also, note
+that @code{(cl-floor @var{x})} is exactly equivalent to
+@code{(cl-floor @var{x} 1)}.
-@example
-(cl-declaim (inline foo bar))
-(cl-eval-when (compile load eval)
- (cl-proclaim '(inline foo bar)))
-(defsubst foo (...) ...) ; instead of defun
-@end example
+This function is entirely compatible with Common Lisp's @code{floor}
+function, except that it returns the two results in a list since
+Emacs Lisp does not support multiple-valued functions.
+@end defun
-@strong{Please note:} this declaration remains in effect after the
-containing source file is done. It is correct to use it to
-request that a function you have defined should be inlined,
-but it is impolite to use it to request inlining of an external
-function.
+@defun cl-ceiling number &optional divisor
+This function implements the Common Lisp @code{ceiling} function,
+which is analogous to @code{floor} except that it rounds the
+argument or quotient of the arguments up toward plus infinity.
+The remainder will be between 0 and minus @var{r}.
+@end defun
-In Common Lisp, it is possible to use @code{(cl-declare (inline @dots{}))}
-before a particular call to a function to cause just that call to
-be inlined; the current byte compilers provide no way to implement
-this, so @code{(cl-declare (inline @dots{}))} is currently ignored by
-this package.
+@defun cl-truncate number &optional divisor
+This function implements the Common Lisp @code{truncate} function,
+which is analogous to @code{floor} except that it rounds the
+argument or quotient of the arguments toward zero. Thus it is
+equivalent to @code{cl-floor} if the argument or quotient is
+positive, or to @code{cl-ceiling} otherwise. The remainder has
+the same sign as @var{number}.
+@end defun
-@item notinline
-The @code{notinline} declaration lists functions which should
-not be inlined after all; it cancels a previous @code{inline}
-declaration.
+@defun cl-round number &optional divisor
+This function implements the Common Lisp @code{round} function,
+which is analogous to @code{floor} except that it rounds the
+argument or quotient of the arguments to the nearest integer.
+In the case of a tie (the argument or quotient is exactly
+halfway between two integers), it rounds to the even integer.
+@end defun
-@item optimize
-This declaration controls how much optimization is performed by
-the compiler. Naturally, it is ignored by the earlier non-optimizing
-compilers.
+@defun cl-mod number divisor
+This function returns the same value as the second return value
+of @code{cl-floor}.
+@end defun
-The word @code{optimize} is followed by any number of lists like
-@code{(speed 3)} or @code{(safety 2)}. Common Lisp defines several
-optimization ``qualities''; this package ignores all but @code{speed}
-and @code{safety}. The value of a quality should be an integer from
-0 to 3, with 0 meaning ``unimportant'' and 3 meaning ``very important''.
-The default level for both qualities is 1.
+@defun cl-rem number divisor
+This function returns the same value as the second return value
+of @code{cl-truncate}.
+@end defun
-In this package, with the optimizing compiler, the
-@code{speed} quality is tied to the @code{byte-optimize}
-flag, which is set to @code{nil} for @code{(speed 0)} and to
-@code{t} for higher settings; and the @code{safety} quality is
-tied to the @code{byte-compile-delete-errors} flag, which is
-set to @code{nil} for @code{(safety 3)} and to @code{t} for all
-lower settings. (The latter flag controls whether the compiler
-is allowed to optimize out code whose only side-effect could
-be to signal an error, e.g., rewriting @code{(progn foo bar)} to
-@code{bar} when it is not known whether @code{foo} will be bound
-at run-time.)
+@node Random Numbers
+@section Random Numbers
-Note that even compiling with @code{(safety 0)}, the Emacs
-byte-code system provides sufficient checking to prevent real
-harm from being done. For example, barring serious bugs in
-Emacs itself, Emacs will not crash with a segmentation fault
-just because of an error in a fully-optimized Lisp program.
+@noindent
+This package also provides an implementation of the Common Lisp
+random number generator. It uses its own additive-congruential
+algorithm, which is much more likely to give statistically clean
+@c FIXME? Still true?
+random numbers than the simple generators supplied by many
+operating systems.
-The @code{optimize} declaration is normally used in a top-level
-@code{cl-proclaim} or @code{cl-declaim} in a file; Common Lisp allows
-it to be used with @code{cl-declare} to set the level of optimization
-locally for a given form, but this will not work correctly with the
-current version of the optimizing compiler. (The @code{cl-declare}
-will set the new optimization level, but that level will not
-automatically be unset after the enclosing form is done.)
+@defun cl-random number &optional state
+This function returns a random nonnegative number less than
+@var{number}, and of the same type (either integer or floating-point).
+The @var{state} argument should be a @code{random-state} object
+that holds the state of the random number generator. The
+function modifies this state object as a side effect. If
+@var{state} is omitted, it defaults to the internal variable
+@code{cl--random-state}, which contains a pre-initialized
+default @code{random-state} object. (Since any number of programs in
+the Emacs process may be accessing @code{cl--random-state} in
+interleaved fashion, the sequence generated from this will be
+irreproducible for all intents and purposes.)
+@end defun
-@item warn
-This declaration controls what sorts of warnings are generated
-by the byte compiler. Again, only the optimizing compiler
-generates warnings. The word @code{warn} is followed by any
-number of ``warning qualities'', similar in form to optimization
-qualities. The currently supported warning types are
-@code{redefine}, @code{callargs}, @code{unresolved}, and
-@code{free-vars}; in the current system, a value of 0 will
-disable these warnings and any higher value will enable them.
-See the documentation for the optimizing byte compiler for details.
-@end table
+@defun cl-make-random-state &optional state
+This function creates or copies a @code{random-state} object.
+If @var{state} is omitted or @code{nil}, it returns a new copy of
+@code{cl--random-state}. This is a copy in the sense that future
+sequences of calls to @code{(cl-random @var{n})} and
+@code{(cl-random @var{n} @var{s})} (where @var{s} is the new
+random-state object) will return identical sequences of random
+numbers.
-@node Symbols
-@chapter Symbols
+If @var{state} is a @code{random-state} object, this function
+returns a copy of that object. If @var{state} is @code{t}, this
+function returns a new @code{random-state} object seeded from the
+date and time. As an extension to Common Lisp, @var{state} may also
+be an integer in which case the new object is seeded from that
+integer; each different integer seed will result in a completely
+different sequence of random numbers.
-@noindent
-This package defines several symbol-related features that were
-missing from Emacs Lisp.
+It is valid to print a @code{random-state} object to a buffer or
+file and later read it back with @code{read}. If a program wishes
+to use a sequence of pseudo-random numbers which can be reproduced
+later for debugging, it can call @code{(cl-make-random-state t)} to
+get a new sequence, then print this sequence to a file. When the
+program is later rerun, it can read the original run's random-state
+from the file.
+@end defun
-@menu
-* Property Lists:: @code{cl-get}, @code{cl-remprop}, @code{cl-getf}, @code{cl-remf}.
-* Creating Symbols:: @code{cl-gensym}, @code{cl-gentemp}.
-@end menu
+@defun cl-random-state-p object
+This predicate returns @code{t} if @var{object} is a
+@code{random-state} object, or @code{nil} otherwise.
+@end defun
-@node Property Lists
-@section Property Lists
+@node Implementation Parameters
+@section Implementation Parameters
@noindent
-These functions augment the standard Emacs Lisp functions @code{get}
-and @code{put} for operating on properties attached to symbols.
-There are also functions for working with property lists as
-first-class data structures not attached to particular symbols.
+This package defines several useful constants having to do with
+floating-point numbers.
-@defun cl-get symbol property &optional default
-This function is like @code{get}, except that if the property is
-not found, the @var{default} argument provides the return value.
-(The Emacs Lisp @code{get} function always uses @code{nil} as
-the default; this package's @code{cl-get} is equivalent to Common
-Lisp's @code{get}.)
+It determines their values by exercising the computer's
+floating-point arithmetic in various ways. Because this operation
+might be slow, the code for initializing them is kept in a separate
+function that must be called before the parameters can be used.
-The @code{cl-get} function is @code{setf}-able; when used in this
-fashion, the @var{default} argument is allowed but ignored.
-@end defun
+@defun cl-float-limits
+This function makes sure that the Common Lisp floating-point parameters
+like @code{cl-most-positive-float} have been initialized. Until it is
+called, these parameters will be @code{nil}.
+@c If this version of Emacs does not support floats, the parameters will
+@c remain @code{nil}.
+If the parameters have already been initialized, the function returns
+immediately.
-@defun cl-remprop symbol property
-This function removes the entry for @var{property} from the property
-list of @var{symbol}. It returns a true value if the property was
-indeed found and removed, or @code{nil} if there was no such property.
-(This function was probably omitted from Emacs originally because,
-since @code{get} did not allow a @var{default}, it was very difficult
-to distinguish between a missing property and a property whose value
-was @code{nil}; thus, setting a property to @code{nil} was close
-enough to @code{cl-remprop} for most purposes.)
+The algorithm makes assumptions that will be valid for almost all
+machines, but will fail if the machine's arithmetic is extremely
+unusual, e.g., decimal.
@end defun
-@defun cl-getf place property &optional default
-This function scans the list @var{place} as if it were a property
-list, i.e., a list of alternating property names and values. If
-an even-numbered element of @var{place} is found which is @code{eq}
-to @var{property}, the following odd-numbered element is returned.
-Otherwise, @var{default} is returned (or @code{nil} if no default
-is given).
-
-In particular,
+Since true Common Lisp supports up to four different floating-point
+precisions, it has families of constants like
+@code{most-positive-single-float}, @code{most-positive-double-float},
+@code{most-positive-long-float}, and so on. Emacs has only one
+floating-point precision, so this package omits the precision word
+from the constants' names.
-@example
-(get sym prop) @equiv{} (cl-get (symbol-plist sym) prop)
-@end example
+@defvar cl-most-positive-float
+This constant equals the largest value a Lisp float can hold.
+For those systems whose arithmetic supports infinities, this is
+the largest @emph{finite} value. For IEEE machines, the value
+is approximately @code{1.79e+308}.
+@end defvar
-It is valid to use @code{getf} as a @code{setf} place, in which case
-its @var{place} argument must itself be a valid @code{setf} place.
-The @var{default} argument, if any, is ignored in this context.
-The effect is to change (via @code{setcar}) the value cell in the
-list that corresponds to @var{property}, or to cons a new property-value
-pair onto the list if the property is not yet present.
+@defvar cl-most-negative-float
+This constant equals the most negative value a Lisp float can hold.
+(It is assumed to be equal to @code{(- cl-most-positive-float)}.)
+@end defvar
-@example
-(put sym prop val) @equiv{} (setf (cl-get (symbol-plist sym) prop) val)
-@end example
+@defvar cl-least-positive-float
+This constant equals the smallest Lisp float value greater than zero.
+For IEEE machines, it is about @code{4.94e-324} if denormals are
+supported or @code{2.22e-308} if not.
+@end defvar
-The @code{get} and @code{cl-get} functions are also @code{setf}-able.
-The fact that @code{default} is ignored can sometimes be useful:
+@defvar cl-least-positive-normalized-float
+This constant equals the smallest @emph{normalized} Lisp float greater
+than zero, i.e., the smallest value for which IEEE denormalization
+will not result in a loss of precision. For IEEE machines, this
+value is about @code{2.22e-308}. For machines that do not support
+the concept of denormalization and gradual underflow, this constant
+will always equal @code{cl-least-positive-float}.
+@end defvar
-@example
-(cl-incf (cl-get 'foo 'usage-count 0))
-@end example
+@defvar cl-least-negative-float
+This constant is the negative counterpart of @code{cl-least-positive-float}.
+@end defvar
-Here, symbol @code{foo}'s @code{usage-count} property is incremented
-if it exists, or set to 1 (an incremented 0) otherwise.
+@defvar cl-least-negative-normalized-float
+This constant is the negative counterpart of
+@code{cl-least-positive-normalized-float}.
+@end defvar
-@c FIXME cl-getf?
-When not used as a @code{setf} form, @code{getf} is just a regular
-function and its @var{place} argument can actually be any Lisp
-expression.
-@end defun
+@defvar cl-float-epsilon
+This constant is the smallest positive Lisp float that can be added
+to 1.0 to produce a distinct value. Adding a smaller number to 1.0
+will yield 1.0 again due to roundoff. For IEEE machines, epsilon
+is about @code{2.22e-16}.
+@end defvar
-@defspec cl-remf place property
-This macro removes the property-value pair for @var{property} from
-the property list stored at @var{place}, which is any @code{setf}-able
-place expression. It returns true if the property was found. Note
-that if @var{property} happens to be first on the list, this will
-effectively do a @code{(setf @var{place} (cddr @var{place}))},
-whereas if it occurs later, this simply uses @code{setcdr} to splice
-out the property and value cells.
-@end defspec
-
-@node Creating Symbols
-@section Creating Symbols
-
-@noindent
-These functions create unique symbols, typically for use as
-temporary variables.
-
-@defun cl-gensym &optional x
-This function creates a new, uninterned symbol (using @code{make-symbol})
-with a unique name. (The name of an uninterned symbol is relevant
-only if the symbol is printed.) By default, the name is generated
-from an increasing sequence of numbers, @samp{G1000}, @samp{G1001},
-@samp{G1002}, etc. If the optional argument @var{x} is a string, that
-string is used as a prefix instead of @samp{G}. Uninterned symbols
-are used in macro expansions for temporary variables, to ensure that
-their names will not conflict with ``real'' variables in the user's
-code.
-@end defun
-
-@defvar cl--gensym-counter
-This variable holds the counter used to generate @code{cl-gensym} names.
-It is incremented after each use by @code{cl-gensym}. In Common Lisp
-this is initialized with 0, but this package initializes it with a
-random (time-dependent) value to avoid trouble when two files that
-each used @code{cl-gensym} in their compilation are loaded together.
-(Uninterned symbols become interned when the compiler writes them
-out to a file and the Emacs loader loads them, so their names have to
-be treated a bit more carefully than in Common Lisp where uninterned
-symbols remain uninterned after loading.)
+@defvar cl-float-negative-epsilon
+This is the smallest positive value that can be subtracted from
+1.0 to produce a distinct value. For IEEE machines, it is about
+@code{1.11e-16}.
@end defvar
-@defun cl-gentemp &optional x
-This function is like @code{cl-gensym}, except that it produces a new
-@emph{interned} symbol. If the symbol that is generated already
-exists, the function keeps incrementing the counter and trying
-again until a new symbol is generated.
-@end defun
-
-This package automatically creates all keywords that are called for by
-@code{&key} argument specifiers, and discourages the use of keywords
-as data unrelated to keyword arguments, so the related function
-@code{defkeyword} (to create self-quoting keyword symbols) is not
-provided.
-
-@node Numbers
-@chapter Numbers
+@node Sequences
+@chapter Sequences
@noindent
-This section defines a few simple Common Lisp operations on numbers
-which were left out of Emacs Lisp.
+Common Lisp defines a number of functions that operate on
+@dfn{sequences}, which are either lists, strings, or vectors.
+Emacs Lisp includes a few of these, notably @code{elt} and
+@code{length}; this package defines most of the rest.
@menu
-* Predicates on Numbers:: @code{cl-plusp}, @code{cl-oddp}, @code{cl-floatp-safe}, etc.
-* Numerical Functions:: @code{abs}, @code{cl-floor}, etc.
-* Random Numbers:: @code{cl-random}, @code{cl-make-random-state}.
-* Implementation Parameters:: @code{cl-most-positive-float}.
+* Sequence Basics:: Arguments shared by all sequence functions.
+* Mapping over Sequences:: @code{cl-mapcar}, @code{cl-map}, @code{cl-maplist}, etc.
+* Sequence Functions:: @code{cl-subseq}, @code{cl-remove}, @code{cl-substitute}, etc.
+* Searching Sequences:: @code{cl-find}, @code{cl-count}, @code{cl-search}, etc.
+* Sorting Sequences:: @code{cl-sort}, @code{cl-stable-sort}, @code{cl-merge}.
@end menu
-@node Predicates on Numbers
-@section Predicates on Numbers
+@node Sequence Basics
+@section Sequence Basics
@noindent
-These functions return @code{t} if the specified condition is
-true of the numerical argument, or @code{nil} otherwise.
+Many of the sequence functions take keyword arguments; @pxref{Argument
+Lists}. All keyword arguments are optional and, if specified,
+may appear in any order.
-@defun cl-plusp number
-This predicate tests whether @var{number} is positive. It is an
-error if the argument is not a number.
-@end defun
+The @code{:key} argument should be passed either @code{nil}, or a
+function of one argument. This key function is used as a filter
+through which the elements of the sequence are seen; for example,
+@code{(cl-find x y :key 'car)} is similar to @code{(cl-assoc x y)}.
+It searches for an element of the list whose @sc{car} equals
+@code{x}, rather than for an element which equals @code{x} itself.
+If @code{:key} is omitted or @code{nil}, the filter is effectively
+the identity function.
-@defun cl-minusp number
-This predicate tests whether @var{number} is negative. It is an
-error if the argument is not a number.
-@end defun
+The @code{:test} and @code{:test-not} arguments should be either
+@code{nil}, or functions of two arguments. The test function is
+used to compare two sequence elements, or to compare a search value
+with sequence elements. (The two values are passed to the test
+function in the same order as the original sequence function
+arguments from which they are derived, or, if they both come from
+the same sequence, in the same order as they appear in that sequence.)
+The @code{:test} argument specifies a function which must return
+true (non-@code{nil}) to indicate a match; instead, you may use
+@code{:test-not} to give a function which returns @emph{false} to
+indicate a match. The default test function is @code{eql}.
-@defun cl-oddp integer
-This predicate tests whether @var{integer} is odd. It is an
-error if the argument is not an integer.
-@end defun
+Many functions that take @var{item} and @code{:test} or @code{:test-not}
+arguments also come in @code{-if} and @code{-if-not} varieties,
+where a @var{predicate} function is passed instead of @var{item},
+and sequence elements match if the predicate returns true on them
+(or false in the case of @code{-if-not}). For example:
-@defun cl-evenp integer
-This predicate tests whether @var{integer} is even. It is an
-error if the argument is not an integer.
-@end defun
+@example
+(cl-remove 0 seq :test '=) @equiv{} (cl-remove-if 'zerop seq)
+@end example
-@defun cl-floatp-safe object
-This predicate tests whether @var{object} is a floating-point
-number. On systems that support floating-point, this is equivalent
-to @code{floatp}. On other systems, this always returns @code{nil}.
-@end defun
+@noindent
+to remove all zeros from sequence @code{seq}.
-@node Numerical Functions
-@section Numerical Functions
+Some operations can work on a subsequence of the argument sequence;
+these function take @code{:start} and @code{:end} arguments, which
+default to zero and the length of the sequence, respectively.
+Only elements between @var{start} (inclusive) and @var{end}
+(exclusive) are affected by the operation. The @var{end} argument
+may be passed @code{nil} to signify the length of the sequence;
+otherwise, both @var{start} and @var{end} must be integers, with
+@code{0 <= @var{start} <= @var{end} <= (length @var{seq})}.
+If the function takes two sequence arguments, the limits are
+defined by keywords @code{:start1} and @code{:end1} for the first,
+and @code{:start2} and @code{:end2} for the second.
-@noindent
-These functions perform various arithmetic operations on numbers.
+A few functions accept a @code{:from-end} argument, which, if
+non-@code{nil}, causes the operation to go from right-to-left
+through the sequence instead of left-to-right, and a @code{:count}
+argument, which specifies an integer maximum number of elements
+to be removed or otherwise processed.
-@defun cl-gcd &rest integers
-This function returns the Greatest Common Divisor of the arguments.
-For one argument, it returns the absolute value of that argument.
-For zero arguments, it returns zero.
-@end defun
+The sequence functions make no guarantees about the order in
+which the @code{:test}, @code{:test-not}, and @code{:key} functions
+are called on various elements. Therefore, it is a bad idea to depend
+on side effects of these functions. For example, @code{:from-end}
+may cause the sequence to be scanned actually in reverse, or it may
+be scanned forwards but computing a result ``as if'' it were scanned
+backwards. (Some functions, like @code{cl-mapcar} and @code{cl-every},
+@emph{do} specify exactly the order in which the function is called
+so side effects are perfectly acceptable in those cases.)
-@defun cl-lcm &rest integers
-This function returns the Least Common Multiple of the arguments.
-For one argument, it returns the absolute value of that argument.
-For zero arguments, it returns one.
-@end defun
+Strings may contain ``text properties'' as well
+as character data. Except as noted, it is undefined whether or
+not text properties are preserved by sequence functions. For
+example, @code{(cl-remove ?A @var{str})} may or may not preserve
+the properties of the characters copied from @var{str} into the
+result.
-@defun cl-isqrt integer
-This function computes the ``integer square root'' of its integer
-argument, i.e., the greatest integer less than or equal to the true
-square root of the argument.
-@end defun
+@node Mapping over Sequences
+@section Mapping over Sequences
-@defun cl-floor number &optional divisor
-With one argument, @code{cl-floor} returns a list of two numbers:
-The argument rounded down (toward minus infinity) to an integer,
-and the ``remainder'' which would have to be added back to the
-first return value to yield the argument again. If the argument
-is an integer @var{x}, the result is always the list @code{(@var{x} 0)}.
-If the argument is a floating-point number, the first
-result is a Lisp integer and the second is a Lisp float between
-0 (inclusive) and 1 (exclusive).
+@noindent
+These functions ``map'' the function you specify over the elements
+of lists or arrays. They are all variations on the theme of the
+built-in function @code{mapcar}.
-With two arguments, @code{cl-floor} divides @var{number} by
-@var{divisor}, and returns the floor of the quotient and the
-corresponding remainder as a list of two numbers. If
-@code{(cl-floor @var{x} @var{y})} returns @code{(@var{q} @var{r})},
-then @code{@var{q}*@var{y} + @var{r} = @var{x}}, with @var{r}
-between 0 (inclusive) and @var{r} (exclusive). Also, note
-that @code{(cl-floor @var{x})} is exactly equivalent to
-@code{(cl-floor @var{x} 1)}.
+@defun cl-mapcar function seq &rest more-seqs
+This function calls @var{function} on successive parallel sets of
+elements from its argument sequences. Given a single @var{seq}
+argument it is equivalent to @code{mapcar}; given @var{n} sequences,
+it calls the function with the first elements of each of the sequences
+as the @var{n} arguments to yield the first element of the result
+list, then with the second elements, and so on. The mapping stops as
+soon as the shortest sequence runs out. The argument sequences may
+be any mixture of lists, strings, and vectors; the return sequence
+is always a list.
-This function is entirely compatible with Common Lisp's @code{floor}
-function, except that it returns the two results in a list since
-Emacs Lisp does not support multiple-valued functions.
+Common Lisp's @code{mapcar} accepts multiple arguments but works
+only on lists; Emacs Lisp's @code{mapcar} accepts a single sequence
+argument. This package's @code{cl-mapcar} works as a compatible
+superset of both.
@end defun
-@defun cl-ceiling number &optional divisor
-This function implements the Common Lisp @code{ceiling} function,
-which is analogous to @code{floor} except that it rounds the
-argument or quotient of the arguments up toward plus infinity.
-The remainder will be between 0 and minus @var{r}.
+@defun cl-map result-type function seq &rest more-seqs
+This function maps @var{function} over the argument sequences,
+just like @code{cl-mapcar}, but it returns a sequence of type
+@var{result-type} rather than a list. @var{result-type} must
+be one of the following symbols: @code{vector}, @code{string},
+@code{list} (in which case the effect is the same as for
+@code{cl-mapcar}), or @code{nil} (in which case the results are
+thrown away and @code{cl-map} returns @code{nil}).
@end defun
-@defun cl-truncate number &optional divisor
-This function implements the Common Lisp @code{truncate} function,
-which is analogous to @code{floor} except that it rounds the
-argument or quotient of the arguments toward zero. Thus it is
-equivalent to @code{cl-floor} if the argument or quotient is
-positive, or to @code{cl-ceiling} otherwise. The remainder has
-the same sign as @var{number}.
+@defun cl-maplist function list &rest more-lists
+This function calls @var{function} on each of its argument lists,
+then on the @sc{cdr}s of those lists, and so on, until the
+shortest list runs out. The results are returned in the form
+of a list. Thus, @code{cl-maplist} is like @code{cl-mapcar} except
+that it passes in the list pointers themselves rather than the
+@sc{car}s of the advancing pointers.
@end defun
-@defun cl-round number &optional divisor
-This function implements the Common Lisp @code{round} function,
-which is analogous to @code{floor} except that it rounds the
-argument or quotient of the arguments to the nearest integer.
-In the case of a tie (the argument or quotient is exactly
-halfway between two integers), it rounds to the even integer.
+@defun cl-mapc function seq &rest more-seqs
+This function is like @code{cl-mapcar}, except that the values returned
+by @var{function} are ignored and thrown away rather than being
+collected into a list. The return value of @code{cl-mapc} is @var{seq},
+the first sequence. This function is more general than the Emacs
+primitive @code{mapc}. (Note that this function is called
+@code{cl-mapc} even in @file{cl.el}, rather than @code{mapc*} as you
+might expect.)
+@c http://debbugs.gnu.org/6575
@end defun
-@defun cl-mod number divisor
-This function returns the same value as the second return value
-of @code{cl-floor}.
+@defun cl-mapl function list &rest more-lists
+This function is like @code{cl-maplist}, except that it throws away
+the values returned by @var{function}.
@end defun
-@defun cl-rem number divisor
-This function returns the same value as the second return value
-of @code{cl-truncate}.
+@defun cl-mapcan function seq &rest more-seqs
+This function is like @code{cl-mapcar}, except that it concatenates
+the return values (which must be lists) using @code{nconc},
+rather than simply collecting them into a list.
@end defun
-@node Random Numbers
-@section Random Numbers
-
-@noindent
-This package also provides an implementation of the Common Lisp
-random number generator. It uses its own additive-congruential
-algorithm, which is much more likely to give statistically clean
-random numbers than the simple generators supplied by many
-operating systems.
-
-@defun cl-random number &optional state
-This function returns a random nonnegative number less than
-@var{number}, and of the same type (either integer or floating-point).
-The @var{state} argument should be a @code{random-state} object
-which holds the state of the random number generator. The
-function modifies this state object as a side effect. If
-@var{state} is omitted, it defaults to the variable
-@code{cl--random-state}, which contains a pre-initialized
-@code{random-state} object.
+@defun cl-mapcon function list &rest more-lists
+This function is like @code{cl-maplist}, except that it concatenates
+the return values using @code{nconc}.
@end defun
-@defvar cl--random-state
-This variable contains the system ``default'' @code{random-state}
-object, used for calls to @code{cl-random} that do not specify an
-alternative state object. Since any number of programs in the
-Emacs process may be accessing @code{cl--random-state} in interleaved
-fashion, the sequence generated from this variable will be
-irreproducible for all intents and purposes.
-@end defvar
-
-@defun cl-make-random-state &optional state
-This function creates or copies a @code{random-state} object.
-If @var{state} is omitted or @code{nil}, it returns a new copy of
-@code{cl--random-state}. This is a copy in the sense that future
-sequences of calls to @code{(cl-random @var{n})} and
-@code{(cl-random @var{n} @var{s})} (where @var{s} is the new
-random-state object) will return identical sequences of random
-numbers.
+@defun cl-some predicate seq &rest more-seqs
+This function calls @var{predicate} on each element of @var{seq}
+in turn; if @var{predicate} returns a non-@code{nil} value,
+@code{cl-some} returns that value, otherwise it returns @code{nil}.
+Given several sequence arguments, it steps through the sequences
+in parallel until the shortest one runs out, just as in
+@code{cl-mapcar}. You can rely on the left-to-right order in which
+the elements are visited, and on the fact that mapping stops
+immediately as soon as @var{predicate} returns non-@code{nil}.
+@end defun
-If @var{state} is a @code{random-state} object, this function
-returns a copy of that object. If @var{state} is @code{t}, this
-function returns a new @code{random-state} object seeded from the
-date and time. As an extension to Common Lisp, @var{state} may also
-be an integer in which case the new object is seeded from that
-integer; each different integer seed will result in a completely
-different sequence of random numbers.
+@defun cl-every predicate seq &rest more-seqs
+This function calls @var{predicate} on each element of the sequence(s)
+in turn; it returns @code{nil} as soon as @var{predicate} returns
+@code{nil} for any element, or @code{t} if the predicate was true
+for all elements.
+@end defun
-It is valid to print a @code{random-state} object to a buffer or
-file and later read it back with @code{read}. If a program wishes
-to use a sequence of pseudo-random numbers which can be reproduced
-later for debugging, it can call @code{(cl-make-random-state t)} to
-get a new sequence, then print this sequence to a file. When the
-program is later rerun, it can read the original run's random-state
-from the file.
+@defun cl-notany predicate seq &rest more-seqs
+This function calls @var{predicate} on each element of the sequence(s)
+in turn; it returns @code{nil} as soon as @var{predicate} returns
+a non-@code{nil} value for any element, or @code{t} if the predicate
+was @code{nil} for all elements.
@end defun
-@defun cl-random-state-p object
-This predicate returns @code{t} if @var{object} is a
-@code{random-state} object, or @code{nil} otherwise.
+@defun cl-notevery predicate seq &rest more-seqs
+This function calls @var{predicate} on each element of the sequence(s)
+in turn; it returns a non-@code{nil} value as soon as @var{predicate}
+returns @code{nil} for any element, or @code{t} if the predicate was
+true for all elements.
@end defun
-@node Implementation Parameters
-@section Implementation Parameters
+@defun cl-reduce function seq @t{&key :from-end :start :end :initial-value :key}
+This function combines the elements of @var{seq} using an associative
+binary operation. Suppose @var{function} is @code{*} and @var{seq} is
+the list @code{(2 3 4 5)}. The first two elements of the list are
+combined with @code{(* 2 3) = 6}; this is combined with the next
+element, @code{(* 6 4) = 24}, and that is combined with the final
+element: @code{(* 24 5) = 120}. Note that the @code{*} function happens
+to be self-reducing, so that @code{(* 2 3 4 5)} has the same effect as
+an explicit call to @code{cl-reduce}.
-@noindent
-This package defines several useful constants having to with numbers.
+If @code{:from-end} is true, the reduction is right-associative instead
+of left-associative:
-The following parameters have to do with floating-point numbers.
-This package determines their values by exercising the computer's
-floating-point arithmetic in various ways. Because this operation
-might be slow, the code for initializing them is kept in a separate
-function that must be called before the parameters can be used.
+@example
+(cl-reduce '- '(1 2 3 4))
+ @equiv{} (- (- (- 1 2) 3) 4) @result{} -8
+(cl-reduce '- '(1 2 3 4) :from-end t)
+ @equiv{} (- 1 (- 2 (- 3 4))) @result{} -2
+@end example
-@defun cl-float-limits
-This function makes sure that the Common Lisp floating-point parameters
-like @code{cl-most-positive-float} have been initialized. Until it is
-called, these parameters will be @code{nil}. If this version of Emacs
-does not support floats, the parameters will remain @code{nil}. If the
-parameters have already been initialized, the function returns
-immediately.
+If @code{:key} is specified, it is a function of one argument, which
+is called on each of the sequence elements in turn.
-The algorithm makes assumptions that will be valid for most modern
-machines, but will fail if the machine's arithmetic is extremely
-unusual, e.g., decimal.
-@end defun
+If @code{:initial-value} is specified, it is effectively added to the
+front (or rear in the case of @code{:from-end}) of the sequence.
+The @code{:key} function is @emph{not} applied to the initial value.
-Since true Common Lisp supports up to four different floating-point
-precisions, it has families of constants like
-@code{most-positive-single-float}, @code{most-positive-double-float},
-@code{most-positive-long-float}, and so on. Emacs has only one
-floating-point precision, so this package omits the precision word
-from the constants' names.
+If the sequence, including the initial value, has exactly one element
+then that element is returned without ever calling @var{function}.
+If the sequence is empty (and there is no initial value), then
+@var{function} is called with no arguments to obtain the return value.
+@end defun
-@defvar cl-most-positive-float
-This constant equals the largest value a Lisp float can hold.
-For those systems whose arithmetic supports infinities, this is
-the largest @emph{finite} value. For IEEE machines, the value
-is approximately @code{1.79e+308}.
-@end defvar
+All of these mapping operations can be expressed conveniently in
+terms of the @code{cl-loop} macro. In compiled code, @code{cl-loop} will
+be faster since it generates the loop as in-line code with no
+function calls.
-@defvar cl-most-negative-float
-This constant equals the most-negative value a Lisp float can hold.
-(It is assumed to be equal to @code{(- cl-most-positive-float)}.)
-@end defvar
+@node Sequence Functions
+@section Sequence Functions
-@defvar cl-least-positive-float
-This constant equals the smallest Lisp float value greater than zero.
-For IEEE machines, it is about @code{4.94e-324} if denormals are
-supported or @code{2.22e-308} if not.
-@end defvar
+@noindent
+This section describes a number of Common Lisp functions for
+operating on sequences.
-@defvar cl-least-positive-normalized-float
-This constant equals the smallest @emph{normalized} Lisp float greater
-than zero, i.e., the smallest value for which IEEE denormalization
-will not result in a loss of precision. For IEEE machines, this
-value is about @code{2.22e-308}. For machines that do not support
-the concept of denormalization and gradual underflow, this constant
-will always equal @code{cl-least-positive-float}.
-@end defvar
+@defun cl-subseq sequence start &optional end
+This function returns a given subsequence of the argument
+@var{sequence}, which may be a list, string, or vector.
+The indices @var{start} and @var{end} must be in range, and
+@var{start} must be no greater than @var{end}. If @var{end}
+is omitted, it defaults to the length of the sequence. The
+return value is always a copy; it does not share structure
+with @var{sequence}.
-@defvar cl-least-negative-float
-This constant is the negative counterpart of @code{cl-least-positive-float}.
-@end defvar
+As an extension to Common Lisp, @var{start} and/or @var{end}
+may be negative, in which case they represent a distance back
+from the end of the sequence. This is for compatibility with
+Emacs's @code{substring} function. Note that @code{cl-subseq} is
+the @emph{only} sequence function that allows negative
+@var{start} and @var{end}.
-@defvar cl-least-negative-normalized-float
-This constant is the negative counterpart of
-@code{cl-least-positive-normalized-float}.
-@end defvar
+You can use @code{setf} on a @code{cl-subseq} form to replace a
+specified range of elements with elements from another sequence.
+The replacement is done as if by @code{cl-replace}, described below.
+@end defun
-@defvar cl-float-epsilon
-This constant is the smallest positive Lisp float that can be added
-to 1.0 to produce a distinct value. Adding a smaller number to 1.0
-will yield 1.0 again due to roundoff. For IEEE machines, epsilon
-is about @code{2.22e-16}.
-@end defvar
+@defun cl-concatenate result-type &rest seqs
+This function concatenates the argument sequences together to
+form a result sequence of type @var{result-type}, one of the
+symbols @code{vector}, @code{string}, or @code{list}. The
+arguments are always copied, even in cases such as
+@code{(cl-concatenate 'list '(1 2 3))} where the result is
+identical to an argument.
+@end defun
-@defvar cl-float-negative-epsilon
-This is the smallest positive value that can be subtracted from
-1.0 to produce a distinct value. For IEEE machines, it is about
-@code{1.11e-16}.
-@end defvar
+@defun cl-fill seq item @t{&key :start :end}
+This function fills the elements of the sequence (or the specified
+part of the sequence) with the value @var{item}.
+@end defun
-@node Sequences
-@chapter Sequences
+@defun cl-replace seq1 seq2 @t{&key :start1 :end1 :start2 :end2}
+This function copies part of @var{seq2} into part of @var{seq1}.
+The sequence @var{seq1} is not stretched or resized; the amount
+of data copied is simply the shorter of the source and destination
+(sub)sequences. The function returns @var{seq1}.
-@noindent
-Common Lisp defines a number of functions that operate on
-@dfn{sequences}, which are either lists, strings, or vectors.
-Emacs Lisp includes a few of these, notably @code{elt} and
-@code{length}; this package defines most of the rest.
+If @var{seq1} and @var{seq2} are @code{eq}, then the replacement
+will work correctly even if the regions indicated by the start
+and end arguments overlap. However, if @var{seq1} and @var{seq2}
+are lists that share storage but are not @code{eq}, and the
+start and end arguments specify overlapping regions, the effect
+is undefined.
+@end defun
-@menu
-* Sequence Basics:: Arguments shared by all sequence functions.
-* Mapping over Sequences:: @code{cl-mapcar}, @code{cl-mapcan}, @code{cl-map}, @code{cl-every}, etc.
-* Sequence Functions:: @code{cl-subseq}, @code{cl-remove}, @code{cl-substitute}, etc.
-* Searching Sequences:: @code{cl-find}, @code{cl-position}, @code{cl-count}, @code{cl-search}, etc.
-* Sorting Sequences:: @code{cl-sort}, @code{cl-stable-sort}, @code{cl-merge}.
-@end menu
+@defun cl-remove item seq @t{&key :test :test-not :key :count :start :end :from-end}
+This returns a copy of @var{seq} with all elements matching
+@var{item} removed. The result may share storage with or be
+@code{eq} to @var{seq} in some circumstances, but the original
+@var{seq} will not be modified. The @code{:test}, @code{:test-not},
+and @code{:key} arguments define the matching test that is used;
+by default, elements @code{eql} to @var{item} are removed. The
+@code{:count} argument specifies the maximum number of matching
+elements that can be removed (only the leftmost @var{count} matches
+are removed). The @code{:start} and @code{:end} arguments specify
+a region in @var{seq} in which elements will be removed; elements
+outside that region are not matched or removed. The @code{:from-end}
+argument, if true, says that elements should be deleted from the
+end of the sequence rather than the beginning (this matters only
+if @var{count} was also specified).
+@end defun
-@node Sequence Basics
-@section Sequence Basics
+@defun cl-delete item seq @t{&key :test :test-not :key :count :start :end :from-end}
+This deletes all elements of @var{seq} that match @var{item}.
+It is a destructive operation. Since Emacs Lisp does not support
+stretchable strings or vectors, this is the same as @code{cl-remove}
+for those sequence types. On lists, @code{cl-remove} will copy the
+list if necessary to preserve the original list, whereas
+@code{cl-delete} will splice out parts of the argument list.
+Compare @code{append} and @code{nconc}, which are analogous
+non-destructive and destructive list operations in Emacs Lisp.
+@end defun
-@noindent
-Many of the sequence functions take keyword arguments; @pxref{Argument
-Lists}. All keyword arguments are optional and, if specified,
-may appear in any order.
+@findex cl-remove-if
+@findex cl-remove-if-not
+@findex cl-delete-if
+@findex cl-delete-if-not
+The predicate-oriented functions @code{cl-remove-if}, @code{cl-remove-if-not},
+@code{cl-delete-if}, and @code{cl-delete-if-not} are defined similarly.
-The @code{:key} argument should be passed either @code{nil}, or a
-function of one argument. This key function is used as a filter
-through which the elements of the sequence are seen; for example,
-@code{(cl-find x y :key 'car)} is similar to @code{(cl-assoc x y)}:
-It searches for an element of the list whose @code{car} equals
-@code{x}, rather than for an element which equals @code{x} itself.
-If @code{:key} is omitted or @code{nil}, the filter is effectively
-the identity function.
-
-The @code{:test} and @code{:test-not} arguments should be either
-@code{nil}, or functions of two arguments. The test function is
-used to compare two sequence elements, or to compare a search value
-with sequence elements. (The two values are passed to the test
-function in the same order as the original sequence function
-arguments from which they are derived, or, if they both come from
-the same sequence, in the same order as they appear in that sequence.)
-The @code{:test} argument specifies a function which must return
-true (non-@code{nil}) to indicate a match; instead, you may use
-@code{:test-not} to give a function which returns @emph{false} to
-indicate a match. The default test function is @code{eql}.
-
-Many functions which take @var{item} and @code{:test} or @code{:test-not}
-arguments also come in @code{-if} and @code{-if-not} varieties,
-where a @var{predicate} function is passed instead of @var{item},
-and sequence elements match if the predicate returns true on them
-(or false in the case of @code{-if-not}). For example:
-
-@example
-(cl-remove 0 seq :test '=) @equiv{} (cl-remove-if 'zerop seq)
-@end example
-
-@noindent
-to remove all zeros from sequence @code{seq}.
+@defun cl-remove-duplicates seq @t{&key :test :test-not :key :start :end :from-end}
+This function returns a copy of @var{seq} with duplicate elements
+removed. Specifically, if two elements from the sequence match
+according to the @code{:test}, @code{:test-not}, and @code{:key}
+arguments, only the rightmost one is retained. If @code{:from-end}
+is true, the leftmost one is retained instead. If @code{:start} or
+@code{:end} is specified, only elements within that subsequence are
+examined or removed.
+@end defun
-Some operations can work on a subsequence of the argument sequence;
-these function take @code{:start} and @code{:end} arguments which
-default to zero and the length of the sequence, respectively.
-Only elements between @var{start} (inclusive) and @var{end}
-(exclusive) are affected by the operation. The @var{end} argument
-may be passed @code{nil} to signify the length of the sequence;
-otherwise, both @var{start} and @var{end} must be integers, with
-@code{0 <= @var{start} <= @var{end} <= (length @var{seq})}.
-If the function takes two sequence arguments, the limits are
-defined by keywords @code{:start1} and @code{:end1} for the first,
-and @code{:start2} and @code{:end2} for the second.
+@defun cl-delete-duplicates seq @t{&key :test :test-not :key :start :end :from-end}
+This function deletes duplicate elements from @var{seq}. It is
+a destructive version of @code{cl-remove-duplicates}.
+@end defun
-A few functions accept a @code{:from-end} argument, which, if
-non-@code{nil}, causes the operation to go from right-to-left
-through the sequence instead of left-to-right, and a @code{:count}
-argument, which specifies an integer maximum number of elements
-to be removed or otherwise processed.
+@defun cl-substitute new old seq @t{&key :test :test-not :key :count :start :end :from-end}
+This function returns a copy of @var{seq}, with all elements
+matching @var{old} replaced with @var{new}. The @code{:count},
+@code{:start}, @code{:end}, and @code{:from-end} arguments may be
+used to limit the number of substitutions made.
+@end defun
-The sequence functions make no guarantees about the order in
-which the @code{:test}, @code{:test-not}, and @code{:key} functions
-are called on various elements. Therefore, it is a bad idea to depend
-on side effects of these functions. For example, @code{:from-end}
-may cause the sequence to be scanned actually in reverse, or it may
-be scanned forwards but computing a result ``as if'' it were scanned
-backwards. (Some functions, like @code{cl-mapcar} and @code{cl-every},
-@emph{do} specify exactly the order in which the function is called
-so side effects are perfectly acceptable in those cases.)
+@defun cl-nsubstitute new old seq @t{&key :test :test-not :key :count :start :end :from-end}
+This is a destructive version of @code{cl-substitute}; it performs
+the substitution using @code{setcar} or @code{aset} rather than
+by returning a changed copy of the sequence.
+@end defun
-Strings may contain ``text properties'' as well
-as character data. Except as noted, it is undefined whether or
-not text properties are preserved by sequence functions. For
-example, @code{(cl-remove ?A @var{str})} may or may not preserve
-the properties of the characters copied from @var{str} into the
-result.
+@findex cl-substitute-if
+@findex cl-substitute-if-not
+@findex cl-nsubstitute-if
+@findex cl-nsubstitute-if-not
+The functions @code{cl-substitute-if}, @code{cl-substitute-if-not},
+@code{cl-nsubstitute-if}, and @code{cl-nsubstitute-if-not} are defined
+similarly. For these, a @var{predicate} is given in place of the
+@var{old} argument.
-@node Mapping over Sequences
-@section Mapping over Sequences
+@node Searching Sequences
+@section Searching Sequences
@noindent
-These functions ``map'' the function you specify over the elements
-of lists or arrays. They are all variations on the theme of the
-built-in function @code{mapcar}.
-
-@defun cl-mapcar function seq &rest more-seqs
-This function calls @var{function} on successive parallel sets of
-elements from its argument sequences. Given a single @var{seq}
-argument it is equivalent to @code{mapcar}; given @var{n} sequences,
-it calls the function with the first elements of each of the sequences
-as the @var{n} arguments to yield the first element of the result
-list, then with the second elements, and so on. The mapping stops as
-soon as the shortest sequence runs out. The argument sequences may
-be any mixture of lists, strings, and vectors; the return sequence
-is always a list.
-
-Common Lisp's @code{mapcar} accepts multiple arguments but works
-only on lists; Emacs Lisp's @code{mapcar} accepts a single sequence
-argument. This package's @code{cl-mapcar} works as a compatible
-superset of both.
-@end defun
-
-@defun cl-map result-type function seq &rest more-seqs
-This function maps @var{function} over the argument sequences,
-just like @code{cl-mapcar}, but it returns a sequence of type
-@var{result-type} rather than a list. @var{result-type} must
-be one of the following symbols: @code{vector}, @code{string},
-@code{list} (in which case the effect is the same as for
-@code{cl-mapcar}), or @code{nil} (in which case the results are
-thrown away and @code{cl-map} returns @code{nil}).
-@end defun
+These functions search for elements or subsequences in a sequence.
+(See also @code{cl-member} and @code{cl-assoc}; @pxref{Lists}.)
-@defun cl-maplist function list &rest more-lists
-This function calls @var{function} on each of its argument lists,
-then on the @code{cdr}s of those lists, and so on, until the
-shortest list runs out. The results are returned in the form
-of a list. Thus, @code{cl-maplist} is like @code{cl-mapcar} except
-that it passes in the list pointers themselves rather than the
-@code{car}s of the advancing pointers.
+@defun cl-find item seq @t{&key :test :test-not :key :start :end :from-end}
+This function searches @var{seq} for an element matching @var{item}.
+If it finds a match, it returns the matching element. Otherwise,
+it returns @code{nil}. It returns the leftmost match, unless
+@code{:from-end} is true, in which case it returns the rightmost
+match. The @code{:start} and @code{:end} arguments may be used to
+limit the range of elements that are searched.
@end defun
-@c FIXME does not exist?
-@defun cl-mapc function seq &rest more-seqs
-This function is like @code{cl-mapcar}, except that the values returned
-by @var{function} are ignored and thrown away rather than being
-collected into a list. The return value of @code{cl-mapc} is @var{seq},
-the first sequence. This function is more general than the Emacs
-primitive @code{mapc}.
+@defun cl-position item seq @t{&key :test :test-not :key :start :end :from-end}
+This function is like @code{cl-find}, except that it returns the
+integer position in the sequence of the matching item rather than
+the item itself. The position is relative to the start of the
+sequence as a whole, even if @code{:start} is non-zero. The function
+returns @code{nil} if no matching element was found.
@end defun
-@defun cl-mapl function list &rest more-lists
-This function is like @code{cl-maplist}, except that it throws away
-the values returned by @var{function}.
+@defun cl-count item seq @t{&key :test :test-not :key :start :end}
+This function returns the number of elements of @var{seq} which
+match @var{item}. The result is always a nonnegative integer.
@end defun
-@defun cl-mapcan function seq &rest more-seqs
-This function is like @code{cl-mapcar}, except that it concatenates
-the return values (which must be lists) using @code{nconc},
-rather than simply collecting them into a list.
-@end defun
+@findex cl-find-if
+@findex cl-find-if-not
+@findex cl-position-if
+@findex cl-position-if-not
+@findex cl-count-if
+@findex cl-count-if-not
+The @code{cl-find-if}, @code{cl-find-if-not}, @code{cl-position-if},
+@code{cl-position-if-not}, @code{cl-count-if}, and @code{cl-count-if-not}
+functions are defined similarly.
-@defun cl-mapcon function list &rest more-lists
-This function is like @code{cl-maplist}, except that it concatenates
-the return values using @code{nconc}.
-@end defun
+@defun cl-mismatch seq1 seq2 @t{&key :test :test-not :key :start1 :end1 :start2 :end2 :from-end}
+This function compares the specified parts of @var{seq1} and
+@var{seq2}. If they are the same length and the corresponding
+elements match (according to @code{:test}, @code{:test-not},
+and @code{:key}), the function returns @code{nil}. If there is
+a mismatch, the function returns the index (relative to @var{seq1})
+of the first mismatching element. This will be the leftmost pair of
+elements that do not match, or the position at which the shorter of
+the two otherwise-matching sequences runs out.
-@defun cl-some predicate seq &rest more-seqs
-This function calls @var{predicate} on each element of @var{seq}
-in turn; if @var{predicate} returns a non-@code{nil} value,
-@code{some} returns that value, otherwise it returns @code{nil}.
-Given several sequence arguments, it steps through the sequences
-in parallel until the shortest one runs out, just as in
-@code{cl-mapcar}. You can rely on the left-to-right order in which
-the elements are visited, and on the fact that mapping stops
-immediately as soon as @var{predicate} returns non-@code{nil}.
-@end defun
+If @code{:from-end} is true, then the elements are compared from right
+to left starting at @code{(1- @var{end1})} and @code{(1- @var{end2})}.
+If the sequences differ, then one plus the index of the rightmost
+difference (relative to @var{seq1}) is returned.
-@defun cl-every predicate seq &rest more-seqs
-This function calls @var{predicate} on each element of the sequence(s)
-in turn; it returns @code{nil} as soon as @var{predicate} returns
-@code{nil} for any element, or @code{t} if the predicate was true
-for all elements.
+An interesting example is @code{(cl-mismatch str1 str2 :key 'upcase)},
+which compares two strings case-insensitively.
@end defun
-@defun cl-notany predicate seq &rest more-seqs
-This function calls @var{predicate} on each element of the sequence(s)
-in turn; it returns @code{nil} as soon as @var{predicate} returns
-a non-@code{nil} value for any element, or @code{t} if the predicate
-was @code{nil} for all elements.
+@defun cl-search seq1 seq2 @t{&key :test :test-not :key :from-end :start1 :end1 :start2 :end2}
+This function searches @var{seq2} for a subsequence that matches
+@var{seq1} (or part of it specified by @code{:start1} and
+@code{:end1}). Only matches that fall entirely within the region
+defined by @code{:start2} and @code{:end2} will be considered.
+The return value is the index of the leftmost element of the
+leftmost match, relative to the start of @var{seq2}, or @code{nil}
+if no matches were found. If @code{:from-end} is true, the
+function finds the @emph{rightmost} matching subsequence.
@end defun
-@defun cl-notevery predicate seq &rest more-seqs
-This function calls @var{predicate} on each element of the sequence(s)
-in turn; it returns a non-@code{nil} value as soon as @var{predicate}
-returns @code{nil} for any element, or @code{t} if the predicate was
-true for all elements.
-@end defun
+@node Sorting Sequences
+@section Sorting Sequences
-@defun cl-reduce function seq @t{&key :from-end :start :end :initial-value :key}
-This function combines the elements of @var{seq} using an associative
-binary operation. Suppose @var{function} is @code{*} and @var{seq} is
-the list @code{(2 3 4 5)}. The first two elements of the list are
-combined with @code{(* 2 3) = 6}; this is combined with the next
-element, @code{(* 6 4) = 24}, and that is combined with the final
-element: @code{(* 24 5) = 120}. Note that the @code{*} function happens
-to be self-reducing, so that @code{(* 2 3 4 5)} has the same effect as
-an explicit call to @code{cl-reduce}.
+@defun cl-sort seq predicate @t{&key :key}
+This function sorts @var{seq} into increasing order as determined
+by using @var{predicate} to compare pairs of elements. @var{predicate}
+should return true (non-@code{nil}) if and only if its first argument
+is less than (not equal to) its second argument. For example,
+@code{<} and @code{string-lessp} are suitable predicate functions
+for sorting numbers and strings, respectively; @code{>} would sort
+numbers into decreasing rather than increasing order.
-If @code{:from-end} is true, the reduction is right-associative instead
-of left-associative:
+This function differs from Emacs's built-in @code{sort} in that it
+can operate on any type of sequence, not just lists. Also, it
+accepts a @code{:key} argument, which is used to preprocess data
+fed to the @var{predicate} function. For example,
@example
-(cl-reduce '- '(1 2 3 4))
- @equiv{} (- (- (- 1 2) 3) 4) @result{} -8
-(cl-reduce '- '(1 2 3 4) :from-end t)
- @equiv{} (- 1 (- 2 (- 3 4))) @result{} -2
+(setq data (cl-sort data 'string-lessp :key 'downcase))
@end example
-If @code{:key} is specified, it is a function of one argument which
-is called on each of the sequence elements in turn.
+@noindent
+sorts @var{data}, a sequence of strings, into increasing alphabetical
+order without regard to case. A @code{:key} function of @code{car}
+would be useful for sorting association lists. It should only be a
+simple accessor though, since it's used heavily in the current
+implementation.
-If @code{:initial-value} is specified, it is effectively added to the
-front (or rear in the case of @code{:from-end}) of the sequence.
-The @code{:key} function is @emph{not} applied to the initial value.
-
-If the sequence, including the initial value, has exactly one element
-then that element is returned without ever calling @var{function}.
-If the sequence is empty (and there is no initial value), then
-@var{function} is called with no arguments to obtain the return value.
-@end defun
-
-All of these mapping operations can be expressed conveniently in
-terms of the @code{cl-loop} macro. In compiled code, @code{cl-loop} will
-be faster since it generates the loop as in-line code with no
-function calls.
-
-@node Sequence Functions
-@section Sequence Functions
-
-@noindent
-This section describes a number of Common Lisp functions for
-operating on sequences.
-
-@defun cl-subseq sequence start &optional end
-This function returns a given subsequence of the argument
-@var{sequence}, which may be a list, string, or vector.
-The indices @var{start} and @var{end} must be in range, and
-@var{start} must be no greater than @var{end}. If @var{end}
-is omitted, it defaults to the length of the sequence. The
-return value is always a copy; it does not share structure
-with @var{sequence}.
-
-As an extension to Common Lisp, @var{start} and/or @var{end}
-may be negative, in which case they represent a distance back
-from the end of the sequence. This is for compatibility with
-Emacs's @code{substring} function. Note that @code{cl-subseq} is
-the @emph{only} sequence function that allows negative
-@var{start} and @var{end}.
-
-You can use @code{setf} on a @code{cl-subseq} form to replace a
-specified range of elements with elements from another sequence.
-The replacement is done as if by @code{cl-replace}, described below.
-@end defun
-
-@defun cl-concatenate result-type &rest seqs
-This function concatenates the argument sequences together to
-form a result sequence of type @var{result-type}, one of the
-symbols @code{vector}, @code{string}, or @code{list}. The
-arguments are always copied, even in cases such as
-@code{(cl-concatenate 'list '(1 2 3))} where the result is
-identical to an argument.
-@end defun
-
-@defun cl-fill seq item @t{&key :start :end}
-This function fills the elements of the sequence (or the specified
-part of the sequence) with the value @var{item}.
-@end defun
-
-@defun cl-replace seq1 seq2 @t{&key :start1 :end1 :start2 :end2}
-This function copies part of @var{seq2} into part of @var{seq1}.
-The sequence @var{seq1} is not stretched or resized; the amount
-of data copied is simply the shorter of the source and destination
-(sub)sequences. The function returns @var{seq1}.
-
-If @var{seq1} and @var{seq2} are @code{eq}, then the replacement
-will work correctly even if the regions indicated by the start
-and end arguments overlap. However, if @var{seq1} and @var{seq2}
-are lists which share storage but are not @code{eq}, and the
-start and end arguments specify overlapping regions, the effect
-is undefined.
-@end defun
-
-@defun cl-remove item seq @t{&key :test :test-not :key :count :start :end :from-end}
-This returns a copy of @var{seq} with all elements matching
-@var{item} removed. The result may share storage with or be
-@code{eq} to @var{seq} in some circumstances, but the original
-@var{seq} will not be modified. The @code{:test}, @code{:test-not},
-and @code{:key} arguments define the matching test that is used;
-by default, elements @code{eql} to @var{item} are removed. The
-@code{:count} argument specifies the maximum number of matching
-elements that can be removed (only the leftmost @var{count} matches
-are removed). The @code{:start} and @code{:end} arguments specify
-a region in @var{seq} in which elements will be removed; elements
-outside that region are not matched or removed. The @code{:from-end}
-argument, if true, says that elements should be deleted from the
-end of the sequence rather than the beginning (this matters only
-if @var{count} was also specified).
-@end defun
-
-@defun cl-delete item seq @t{&key :test :test-not :key :count :start :end :from-end}
-This deletes all elements of @var{seq} which match @var{item}.
-It is a destructive operation. Since Emacs Lisp does not support
-stretchable strings or vectors, this is the same as @code{cl-remove}
-for those sequence types. On lists, @code{cl-remove} will copy the
-list if necessary to preserve the original list, whereas
-@code{cl-delete} will splice out parts of the argument list.
-Compare @code{append} and @code{nconc}, which are analogous
-non-destructive and destructive list operations in Emacs Lisp.
-@end defun
-
-@findex cl-remove-if
-@findex cl-remove-if-not
-@findex cl-delete-if
-@findex cl-delete-if-not
-The predicate-oriented functions @code{cl-remove-if}, @code{cl-remove-if-not},
-@code{cl-delete-if}, and @code{cl-delete-if-not} are defined similarly.
-
-@defun cl-remove-duplicates seq @t{&key :test :test-not :key :start :end :from-end}
-This function returns a copy of @var{seq} with duplicate elements
-removed. Specifically, if two elements from the sequence match
-according to the @code{:test}, @code{:test-not}, and @code{:key}
-arguments, only the rightmost one is retained. If @code{:from-end}
-is true, the leftmost one is retained instead. If @code{:start} or
-@code{:end} is specified, only elements within that subsequence are
-examined or removed.
-@end defun
-
-@defun cl-delete-duplicates seq @t{&key :test :test-not :key :start :end :from-end}
-This function deletes duplicate elements from @var{seq}. It is
-a destructive version of @code{cl-remove-duplicates}.
-@end defun
-
-@defun cl-substitute new old seq @t{&key :test :test-not :key :count :start :end :from-end}
-This function returns a copy of @var{seq}, with all elements
-matching @var{old} replaced with @var{new}. The @code{:count},
-@code{:start}, @code{:end}, and @code{:from-end} arguments may be
-used to limit the number of substitutions made.
-@end defun
-
-@defun cl-nsubstitute new old seq @t{&key :test :test-not :key :count :start :end :from-end}
-This is a destructive version of @code{cl-substitute}; it performs
-the substitution using @code{setcar} or @code{aset} rather than
-by returning a changed copy of the sequence.
-@end defun
-
-@findex cl-substitute-if
-@findex cl-substitute-if-not
-@findex cl-nsubstitute-if
-@findex cl-nsubstitute-if-not
-The functions @code{cl-substitute-if}, @code{cl-substitute-if-not},
-@code{cl-nsubstitute-if}, and @code{cl-nsubstitute-if-not} are defined
-similarly. For these, a @var{predicate} is given in place of the
-@var{old} argument.
-
-@node Searching Sequences
-@section Searching Sequences
-
-@noindent
-These functions search for elements or subsequences in a sequence.
-(See also @code{cl-member} and @code{cl-assoc}; @pxref{Lists}.)
-
-@defun cl-find item seq @t{&key :test :test-not :key :start :end :from-end}
-This function searches @var{seq} for an element matching @var{item}.
-If it finds a match, it returns the matching element. Otherwise,
-it returns @code{nil}. It returns the leftmost match, unless
-@code{:from-end} is true, in which case it returns the rightmost
-match. The @code{:start} and @code{:end} arguments may be used to
-limit the range of elements that are searched.
-@end defun
-
-@defun cl-position item seq @t{&key :test :test-not :key :start :end :from-end}
-This function is like @code{cl-find}, except that it returns the
-integer position in the sequence of the matching item rather than
-the item itself. The position is relative to the start of the
-sequence as a whole, even if @code{:start} is non-zero. The function
-returns @code{nil} if no matching element was found.
-@end defun
-
-@defun cl-count item seq @t{&key :test :test-not :key :start :end}
-This function returns the number of elements of @var{seq} which
-match @var{item}. The result is always a nonnegative integer.
-@end defun
-
-@findex cl-find-if
-@findex cl-find-if-not
-@findex cl-position-if
-@findex cl-position-if-not
-@findex cl-count-if
-@findex cl-count-if-not
-The @code{cl-find-if}, @code{cl-find-if-not}, @code{cl-position-if},
-@code{cl-position-if-not}, @code{cl-count-if}, and @code{cl-count-if-not}
-functions are defined similarly.
-
-@defun cl-mismatch seq1 seq2 @t{&key :test :test-not :key :start1 :end1 :start2 :end2 :from-end}
-This function compares the specified parts of @var{seq1} and
-@var{seq2}. If they are the same length and the corresponding
-elements match (according to @code{:test}, @code{:test-not},
-and @code{:key}), the function returns @code{nil}. If there is
-a mismatch, the function returns the index (relative to @var{seq1})
-of the first mismatching element. This will be the leftmost pair of
-elements which do not match, or the position at which the shorter of
-the two otherwise-matching sequences runs out.
-
-If @code{:from-end} is true, then the elements are compared from right
-to left starting at @code{(1- @var{end1})} and @code{(1- @var{end2})}.
-If the sequences differ, then one plus the index of the rightmost
-difference (relative to @var{seq1}) is returned.
-
-An interesting example is @code{(cl-mismatch str1 str2 :key 'upcase)},
-which compares two strings case-insensitively.
-@end defun
-
-@defun cl-search seq1 seq2 @t{&key :test :test-not :key :from-end :start1 :end1 :start2 :end2}
-This function searches @var{seq2} for a subsequence that matches
-@var{seq1} (or part of it specified by @code{:start1} and
-@code{:end1}.) Only matches which fall entirely within the region
-defined by @code{:start2} and @code{:end2} will be considered.
-The return value is the index of the leftmost element of the
-leftmost match, relative to the start of @var{seq2}, or @code{nil}
-if no matches were found. If @code{:from-end} is true, the
-function finds the @emph{rightmost} matching subsequence.
-@end defun
-
-@node Sorting Sequences
-@section Sorting Sequences
-
-@defun clsort seq predicate @t{&key :key}
-This function sorts @var{seq} into increasing order as determined
-by using @var{predicate} to compare pairs of elements. @var{predicate}
-should return true (non-@code{nil}) if and only if its first argument
-is less than (not equal to) its second argument. For example,
-@code{<} and @code{string-lessp} are suitable predicate functions
-for sorting numbers and strings, respectively; @code{>} would sort
-numbers into decreasing rather than increasing order.
-
-This function differs from Emacs's built-in @code{sort} in that it
-can operate on any type of sequence, not just lists. Also, it
-accepts a @code{:key} argument which is used to preprocess data
-fed to the @var{predicate} function. For example,
-
-@example
-(setq data (cl-sort data 'string-lessp :key 'downcase))
-@end example
-
-@noindent
-sorts @var{data}, a sequence of strings, into increasing alphabetical
-order without regard to case. A @code{:key} function of @code{car}
-would be useful for sorting association lists. It should only be a
-simple accessor though, it's used heavily in the current
-implementation.
-
-The @code{cl-sort} function is destructive; it sorts lists by actually
-rearranging the @code{cdr} pointers in suitable fashion.
-@end defun
+The @code{cl-sort} function is destructive; it sorts lists by actually
+rearranging the @sc{cdr} pointers in suitable fashion.
+@end defun
@defun cl-stable-sort seq predicate @t{&key :key}
This function sorts @var{seq} @dfn{stably}, meaning two elements
* List Functions:: @code{cl-caddr}, @code{cl-first}, @code{cl-list*}, etc.
* Substitution of Expressions:: @code{cl-subst}, @code{cl-sublis}, etc.
* Lists as Sets:: @code{cl-member}, @code{cl-adjoin}, @code{cl-union}, etc.
-* Association Lists:: @code{cl-assoc}, @code{cl-rassoc}, @code{cl-acons}, @code{cl-pairlis}.
+* Association Lists:: @code{cl-assoc}, @code{cl-acons}, @code{cl-pairlis}, etc.
@end menu
@node List Functions
@defun cl-caddr x
This function is equivalent to @code{(car (cdr (cdr @var{x})))}.
-Likewise, this package defines all 28 @code{c@var{xxx}r} functions
+Likewise, this package defines all 24 @code{c@var{xxx}r} functions
where @var{xxx} is up to four @samp{a}s and/or @samp{d}s.
All of these functions are @code{setf}-able, and calls to them
are expanded inline by the byte-compiler for maximum efficiency.
@defun cl-list-length x
This function returns the length of list @var{x}, exactly like
@code{(length @var{x})}, except that if @var{x} is a circular
-list (where the cdr-chain forms a loop rather than terminating
+list (where the @sc{cdr}-chain forms a loop rather than terminating
with @code{nil}), this function returns @code{nil}. (The regular
-@code{length} function would get stuck if given a circular list.)
+@code{length} function would get stuck if given a circular list.
+See also the @code{safe-length} function.)
@end defun
@defun cl-list* arg &rest others
This function constructs a list of its arguments. The final
-argument becomes the @code{cdr} of the last cell constructed.
+argument becomes the @sc{cdr} of the last cell constructed.
Thus, @code{(cl-list* @var{a} @var{b} @var{c})} is equivalent to
@code{(cons @var{a} (cons @var{b} @var{c}))}, and
@code{(cl-list* @var{a} @var{b} nil)} is equivalent to
dotted lists like @code{(1 2 . 3)} correctly.
@end defun
-@defun copy-tree x &optional vecp
-This function returns a copy of the tree of cons cells @var{x}.
-@c FIXME? cl-copy-list is not an alias of copy-sequence.
-Unlike @code{copy-sequence} (and its alias @code{cl-copy-list}),
-which copies only along the @code{cdr} direction, this function
-copies (recursively) along both the @code{car} and the @code{cdr}
-directions. If @var{x} is not a cons cell, the function simply
-returns @var{x} unchanged. If the optional @var{vecp} argument
-is true, this function copies vectors (recursively) as well as
-cons cells.
-@end defun
-
@defun cl-tree-equal x y @t{&key :test :test-not :key}
This function compares two trees of cons cells. If @var{x} and
-@var{y} are both cons cells, their @code{car}s and @code{cdr}s are
+@var{y} are both cons cells, their @sc{car}s and @sc{cdr}s are
compared recursively. If neither @var{x} nor @var{y} is a cons
cell, they are compared by @code{eql}, or according to the
specified test. The @code{:key} function, if specified, is
tree, which will be a copy except that it may share storage with
the argument @var{tree} in parts where no substitutions occurred.
The original @var{tree} is not modified. This function recurses
-on, and compares against @var{old}, both @code{car}s and @code{cdr}s
+on, and compares against @var{old}, both @sc{car}s and @sc{cdr}s
of the component cons cells. If @var{old} is itself a cons cell,
then matching cells in the tree are substituted as usual without
recursively substituting in that cell. Comparisons with @var{old}
This function is like @code{cl-subst}, except that it takes an
association list @var{alist} of @var{old}-@var{new} pairs.
Each element of the tree (after applying the @code{:key}
-function, if any), is compared with the @code{car}s of
+function, if any), is compared with the @sc{car}s of
@var{alist}; if it matches, it is replaced by the corresponding
-@code{cdr}.
+@sc{cdr}.
@end defun
@defun cl-nsublis alist tree @t{&key :test :test-not :key}
@section Lists as Sets
@noindent
-These functions perform operations on lists which represent sets
+These functions perform operations on lists that represent sets
of elements.
@defun cl-member item list @t{&key :test :test-not :key}
This function searches @var{list} for an element matching @var{item}.
-If a match is found, it returns the cons cell whose @code{car} was
+If a match is found, it returns the cons cell whose @sc{car} was
the matching element. Otherwise, it returns @code{nil}. Elements
are compared by @code{eql} by default; you can use the @code{:test},
@code{:test-not}, and @code{:key} arguments to modify this behavior.
The standard Emacs lisp function @code{member} uses @code{equal} for
comparisons; it is equivalent to @code{(cl-member @var{item} @var{list}
-:test 'equal)}.
+:test 'equal)}. With no keyword arguments, @code{cl-member} is
+equivalent to @code{memq}.
@end defun
@findex cl-member-if
@findex cl-member-if-not
The @code{cl-member-if} and @code{cl-member-if-not} functions
-analogously search for elements which satisfy a given predicate.
+analogously search for elements that satisfy a given predicate.
@defun cl-tailp sublist list
This function returns @code{t} if @var{sublist} is a sublist of
@var{list}, i.e., if @var{sublist} is @code{eql} to @var{list} or to
-any of its @code{cdr}s.
+any of its @sc{cdr}s.
@end defun
@defun cl-adjoin item list @t{&key :test :test-not :key}
@end defun
@defun cl-union list1 list2 @t{&key :test :test-not :key}
-This function combines two lists which represent sets of items,
+This function combines two lists that represent sets of items,
returning a list that represents the union of those two sets.
-The result list will contain all items which appear in @var{list1}
+The resulting list contains all items that appear in @var{list1}
or @var{list2}, and no others. If an item appears in both
-@var{list1} and @var{list2} it will be copied only once. If
+@var{list1} and @var{list2} it is copied only once. If
an item is duplicated in @var{list1} or @var{list2}, it is
undefined whether or not that duplication will survive in the
result list. The order of elements in the result list is also
@defun cl-intersection list1 list2 @t{&key :test :test-not :key}
This function computes the intersection of the sets represented
by @var{list1} and @var{list2}. It returns the list of items
-which appear in both @var{list1} and @var{list2}.
+that appear in both @var{list1} and @var{list2}.
@end defun
@defun cl-nintersection list1 list2 @t{&key :test :test-not :key}
@defun cl-assoc item a-list @t{&key :test :test-not :key}
This function searches the association list @var{a-list} for an
-element whose @code{car} matches (in the sense of @code{:test},
+element whose @sc{car} matches (in the sense of @code{:test},
@code{:test-not}, and @code{:key}, or by comparison with @code{eql})
a given @var{item}. It returns the matching element, if any,
-otherwise @code{nil}. It ignores elements of @var{a-list} which
+otherwise @code{nil}. It ignores elements of @var{a-list} that
are not cons cells. (This corresponds to the behavior of
@code{assq} and @code{assoc} in Emacs Lisp; Common Lisp's
@code{assoc} ignores @code{nil}s but considers any other non-cons
@end defun
@defun cl-rassoc item a-list @t{&key :test :test-not :key}
-This function searches for an element whose @code{cdr} matches
+This function searches for an element whose @sc{cdr} matches
@var{item}. If @var{a-list} represents a mapping, this applies
the inverse of the mapping to @var{item}.
@end defun
implements structures as vectors (or lists upon request) with a
special ``tag'' symbol to identify them.
-@defspec cl-defstruct name slots@dots{}
+@defmac cl-defstruct name slots@dots{}
The @code{cl-defstruct} form defines a new structure type called
@var{name}, with the specified @var{slots}. (The @var{slots}
may begin with a string which documents the structure type.)
@end example
@noindent
-defines a struct type called @code{person} which contains three
+defines a struct type called @code{person} that contains three
slots. Given a @code{person} object @var{p}, you can access those
slots by calling @code{(person-name @var{p})}, @code{(person-age @var{p})},
and @code{(person-sex @var{p})}. You can also change these slots by
-using @code{setf} on any of these place forms:
+using @code{setf} on any of these place forms, for example:
@example
(cl-incf (person-age birthday-boy))
object of the same type whose slots are @code{eq} to those of @var{p}.
Given any Lisp object @var{x}, @code{(person-p @var{x})} returns
-true if @var{x} looks like a @code{person}, false otherwise. (Again,
+true if @var{x} looks like a @code{person}, and false otherwise. (Again,
in Common Lisp this predicate would be exact; in Emacs Lisp the
best it can do is verify that @var{x} is a vector of the correct
-length which starts with the correct tag symbol.)
+length that starts with the correct tag symbol.)
Accessors like @code{person-name} normally check their arguments
(effectively using @code{person-p}) and signal an error if the
symbol followed by any number of @dfn{struct options}; each @var{slot}
is either a slot symbol or a list of the form @samp{(@var{slot-name}
@var{default-value} @var{slot-options}@dots{})}. The @var{default-value}
-is a Lisp form which is evaluated any time an instance of the
+is a Lisp form that is evaluated any time an instance of the
structure type is created without specifying that slot's value.
Common Lisp defines several slot options, but the only one
initialized from the corresponding argument. Slots whose names
do not appear in the argument list are initialized based on the
@var{default-value} in their slot descriptor. Also, @code{&optional}
-and @code{&key} arguments which don't specify defaults take their
+and @code{&key} arguments that don't specify defaults take their
defaults from the slot descriptor. It is valid to include arguments
-which don't correspond to slot names; these are useful if they are
+that don't correspond to slot names; these are useful if they are
referred to in the defaults for optional, keyword, or @code{&aux}
-arguments which @emph{do} correspond to slots.
+arguments that @emph{do} correspond to slots.
You can specify any number of full-format @code{:constructor}
options on a structure. The default constructor is still generated
all copier functions are simply synonyms for @code{copy-sequence}.)
@item :predicate
-The argument is an alternate name for the predicate which recognizes
+The argument is an alternate name for the predicate that recognizes
objects of this type. The default is @code{@var{name}-p}. @code{nil}
means not to generate a predicate function. (If the @code{:type}
option is used without the @code{:named} option, no predicate is
@item :print-function
In full Common Lisp, this option allows you to specify a function
-which is called to print an instance of the structure type. The
+that is called to print an instance of the structure type. The
Emacs Lisp system offers no hooks into the Lisp printer which would
allow for such a feature, so this package simply ignores
@code{:print-function}.
specifies a number of slots to be skipped between the last slot
of the included type and the first new slot.
@end table
-@end defspec
+@end defmac
Except as noted, the @code{cl-defstruct} facility of this package is
entirely compatible with that of Common Lisp.
away the following assertions. Because assertions might be optimized
away, it is a bad idea for them to include side-effects.
-@defspec cl-assert test-form [show-args string args@dots{}]
+@defmac cl-assert test-form [show-args string args@dots{}]
This form verifies that @var{test-form} is true (i.e., evaluates to
a non-@code{nil} value). If so, it returns @code{nil}. If the test
is not satisfied, @code{cl-assert} signals an error.
argument plus optional extra arguments. Those arguments are simply
passed to @code{error} to signal the error.
-If the optional second argument @var{show-args} is @code{t} instead
-of @code{nil}, then the error message (with or without @var{string})
-will also include all non-constant arguments of the top-level
-@var{form}. For example:
+If the optional second argument @var{show-args} is @code{t} instead
+of @code{nil}, then the error message (with or without @var{string})
+will also include all non-constant arguments of the top-level
+@var{form}. For example:
+
+@example
+(cl-assert (> x 10) t "x is too small: %d")
+@end example
+
+This usage of @var{show-args} is an extension to Common Lisp. In
+true Common Lisp, the second argument gives a list of @var{places}
+which can be @code{setf}'d by the user before continuing from the
+error. Since Emacs Lisp does not support continuable errors, it
+makes no sense to specify @var{places}.
+@end defmac
+
+@defmac cl-check-type form type [string]
+This form verifies that @var{form} evaluates to a value of type
+@var{type}. If so, it returns @code{nil}. If not, @code{cl-check-type}
+signals a @code{wrong-type-argument} error. The default error message
+lists the erroneous value along with @var{type} and @var{form}
+themselves. If @var{string} is specified, it is included in the
+error message in place of @var{type}. For example:
+
+@example
+(cl-check-type x (integer 1 *) "a positive integer")
+@end example
+
+@xref{Type Predicates}, for a description of the type specifiers
+that may be used for @var{type}.
+
+Note that in Common Lisp, the first argument to @code{check-type}
+must be a @var{place} suitable for use by @code{setf}, because
+@code{check-type} signals a continuable error that allows the
+user to modify @var{place}.
+@end defmac
+
+@node Efficiency Concerns
+@appendix Efficiency Concerns
+
+@appendixsec Macros
+
+@noindent
+Many of the advanced features of this package, such as @code{cl-defun},
+@code{cl-loop}, etc., are implemented as Lisp macros. In
+byte-compiled code, these complex notations will be expanded into
+equivalent Lisp code which is simple and efficient. For example,
+the form
+
+@example
+(cl-incf i n)
+@end example
+
+@noindent
+is expanded at compile-time to the Lisp form
+
+@example
+(setq i (+ i n))
+@end example
+
+@noindent
+which is the most efficient ways of doing this operation
+in Lisp. Thus, there is no performance penalty for using the more
+readable @code{cl-incf} form in your compiled code.
+
+@emph{Interpreted} code, on the other hand, must expand these macros
+every time they are executed. For this reason it is strongly
+recommended that code making heavy use of macros be compiled.
+A loop using @code{cl-incf} a hundred times will execute considerably
+faster if compiled, and will also garbage-collect less because the
+macro expansion will not have to be generated, used, and thrown away a
+hundred times.
+
+You can find out how a macro expands by using the
+@code{cl-prettyexpand} function.
+
+@defun cl-prettyexpand form &optional full
+This function takes a single Lisp form as an argument and inserts
+a nicely formatted copy of it in the current buffer (which must be
+in Lisp mode so that indentation works properly). It also expands
+all Lisp macros that appear in the form. The easiest way to use
+this function is to go to the @file{*scratch*} buffer and type, say,
+
+@example
+(cl-prettyexpand '(cl-loop for x below 10 collect x))
+@end example
+
+@noindent
+and type @kbd{C-x C-e} immediately after the closing parenthesis;
+an expansion similar to:
+
+@example
+(cl-block nil
+ (let* ((x 0)
+ (G1004 nil))
+ (while (< x 10)
+ (setq G1004 (cons x G1004))
+ (setq x (+ x 1)))
+ (nreverse G1004)))
+@end example
+
+@noindent
+will be inserted into the buffer. (The @code{cl-block} macro is
+expanded differently in the interpreter and compiler, so
+@code{cl-prettyexpand} just leaves it alone. The temporary
+variable @code{G1004} was created by @code{cl-gensym}.)
+
+If the optional argument @var{full} is true, then @emph{all}
+macros are expanded, including @code{cl-block}, @code{cl-eval-when},
+and compiler macros. Expansion is done as if @var{form} were
+a top-level form in a file being compiled.
+
+@c FIXME none of these examples are still applicable.
+@ignore
+For example,
+
+@example
+(cl-prettyexpand '(cl-pushnew 'x list))
+ @print{} (setq list (cl-adjoin 'x list))
+(cl-prettyexpand '(cl-pushnew 'x list) t)
+ @print{} (setq list (if (memq 'x list) list (cons 'x list)))
+(cl-prettyexpand '(caddr (cl-member 'a list)) t)
+ @print{} (car (cdr (cdr (memq 'a list))))
+@end example
+@end ignore
+
+Note that @code{cl-adjoin}, @code{cl-caddr}, and @code{cl-member} all
+have built-in compiler macros to optimize them in common cases.
+@end defun
+
+@appendixsec Error Checking
+
+@noindent
+Common Lisp compliance has in general not been sacrificed for the
+sake of efficiency. A few exceptions have been made for cases
+where substantial gains were possible at the expense of marginal
+incompatibility.
+
+The Common Lisp standard (as embodied in Steele's book) uses the
+phrase ``it is an error if'' to indicate a situation that is not
+supposed to arise in complying programs; implementations are strongly
+encouraged but not required to signal an error in these situations.
+This package sometimes omits such error checking in the interest of
+compactness and efficiency. For example, @code{cl-do} variable
+specifiers are supposed to be lists of one, two, or three forms;
+extra forms are ignored by this package rather than signaling a
+syntax error. The @code{cl-endp} function is simply a synonym for
+@code{null} in this package. Functions taking keyword arguments
+will accept an odd number of arguments, treating the trailing
+keyword as if it were followed by the value @code{nil}.
+
+Argument lists (as processed by @code{cl-defun} and friends)
+@emph{are} checked rigorously except for the minor point just
+mentioned; in particular, keyword arguments are checked for
+validity, and @code{&allow-other-keys} and @code{:allow-other-keys}
+are fully implemented. Keyword validity checking is slightly
+time consuming (though not too bad in byte-compiled code);
+you can use @code{&allow-other-keys} to omit this check. Functions
+defined in this package such as @code{cl-find} and @code{cl-member}
+do check their keyword arguments for validity.
+
+@appendixsec Compiler Optimizations
+
+@noindent
+Changing the value of @code{byte-optimize} from the default @code{t}
+is highly discouraged; many of the Common
+Lisp macros emit
+code that can be improved by optimization. In particular,
+@code{cl-block}s (whether explicit or implicit in constructs like
+@code{cl-defun} and @code{cl-loop}) carry a fair run-time penalty; the
+byte-compiler removes @code{cl-block}s that are not actually
+referenced by @code{cl-return} or @code{cl-return-from} inside the block.
+
+@node Common Lisp Compatibility
+@appendix Common Lisp Compatibility
+
+@noindent
+The following is a list of all known incompatibilities between this
+package and Common Lisp as documented in Steele (2nd edition).
+
+The word @code{cl-defun} is required instead of @code{defun} in order
+to use extended Common Lisp argument lists in a function. Likewise,
+@code{cl-defmacro} and @code{cl-function} are versions of those forms
+which understand full-featured argument lists. The @code{&whole}
+keyword does not work in @code{cl-defmacro} argument lists (except
+inside recursive argument lists).
+
+The @code{equal} predicate does not distinguish
+between IEEE floating-point plus and minus zero. The @code{cl-equalp}
+predicate has several differences with Common Lisp; @pxref{Predicates}.
+
+The @code{cl-do-all-symbols} form is the same as @code{cl-do-symbols}
+with no @var{obarray} argument. In Common Lisp, this form would
+iterate over all symbols in all packages. Since Emacs obarrays
+are not a first-class package mechanism, there is no way for
+@code{cl-do-all-symbols} to locate any but the default obarray.
+
+The @code{cl-loop} macro is complete except that @code{loop-finish}
+and type specifiers are unimplemented.
+
+The multiple-value return facility treats lists as multiple
+values, since Emacs Lisp cannot support multiple return values
+directly. The macros will be compatible with Common Lisp if
+@code{cl-values} or @code{cl-values-list} is always used to return to
+a @code{cl-multiple-value-bind} or other multiple-value receiver;
+if @code{cl-values} is used without @code{cl-multiple-value-@dots{}}
+or vice-versa the effect will be different from Common Lisp.
+
+Many Common Lisp declarations are ignored, and others match
+the Common Lisp standard in concept but not in detail. For
+example, local @code{special} declarations, which are purely
+advisory in Emacs Lisp, do not rigorously obey the scoping rules
+set down in Steele's book.
+
+The variable @code{cl--gensym-counter} starts out with a pseudo-random
+value rather than with zero. This is to cope with the fact that
+generated symbols become interned when they are written to and
+loaded back from a file.
+
+The @code{cl-defstruct} facility is compatible, except that structures
+are of type @code{:type vector :named} by default rather than some
+special, distinct type. Also, the @code{:type} slot option is ignored.
+
+The second argument of @code{cl-check-type} is treated differently.
+
+@node Porting Common Lisp
+@appendix Porting Common Lisp
+
+@noindent
+This package is meant to be used as an extension to Emacs Lisp,
+not as an Emacs implementation of true Common Lisp. Some of the
+remaining differences between Emacs Lisp and Common Lisp make it
+difficult to port large Common Lisp applications to Emacs. For
+one, some of the features in this package are not fully compliant
+with ANSI or Steele; @pxref{Common Lisp Compatibility}. But there
+are also quite a few features that this package does not provide
+at all. Here are some major omissions that you will want to watch out
+for when bringing Common Lisp code into Emacs.
+
+@itemize @bullet
+@item
+Case-insensitivity. Symbols in Common Lisp are case-insensitive
+by default. Some programs refer to a function or variable as
+@code{foo} in one place and @code{Foo} or @code{FOO} in another.
+Emacs Lisp will treat these as three distinct symbols.
+
+Some Common Lisp code is written entirely in upper case. While Emacs
+is happy to let the program's own functions and variables use
+this convention, calls to Lisp builtins like @code{if} and
+@code{defun} will have to be changed to lower case.
+
+@item
+Lexical scoping. In Common Lisp, function arguments and @code{let}
+bindings apply only to references physically within their bodies (or
+within macro expansions in their bodies). Traditionally, Emacs Lisp
+uses @dfn{dynamic scoping} wherein a binding to a variable is visible
+even inside functions called from the body.
+@xref{Dynamic Binding,,,elisp,GNU Emacs Lisp Reference Manual}.
+Lexical binding is available since Emacs 24.1, so be sure to set
+@code{lexical-binding} to @code{t} if you need to emulate this aspect
+of Common Lisp. @xref{Lexical Binding,,,elisp,GNU Emacs Lisp Reference Manual}.
+
+Here is an example of a Common Lisp code fragment that would fail in
+Emacs Lisp if @code{lexical-binding} were set to @code{nil}:
+
+@example
+(defun map-odd-elements (func list)
+ (loop for x in list
+ for flag = t then (not flag)
+ collect (if flag x (funcall func x))))
+
+(defun add-odd-elements (list x)
+ (map-odd-elements (lambda (a) (+ a x)) list))
+@end example
+
+@noindent
+With lexical binding, the two functions' usages of @code{x} are
+completely independent. With dynamic binding, the binding to @code{x}
+made by @code{add-odd-elements} will have been hidden by the binding
+in @code{map-odd-elements} by the time the @code{(+ a x)} function is
+called.
+
+Internally, this package uses lexical binding so that such problems do
+not occur. @xref{Obsolete Lexical Binding}, for a description of the obsolete
+@code{lexical-let} form that emulates a Common Lisp-style lexical
+binding when dynamic binding is in use.
+
+@item
+Reader macros. Common Lisp includes a second type of macro that
+works at the level of individual characters. For example, Common
+Lisp implements the quote notation by a reader macro called @code{'},
+whereas Emacs Lisp's parser just treats quote as a special case.
+Some Lisp packages use reader macros to create special syntaxes
+for themselves, which the Emacs parser is incapable of reading.
+
+@item
+Other syntactic features. Common Lisp provides a number of
+notations beginning with @code{#} that the Emacs Lisp parser
+won't understand. For example, @samp{#| @dots{} |#} is an
+alternate comment notation, and @samp{#+lucid (foo)} tells
+the parser to ignore the @code{(foo)} except in Lucid Common
+Lisp.
+
+@item
+Packages. In Common Lisp, symbols are divided into @dfn{packages}.
+Symbols that are Lisp built-ins are typically stored in one package;
+symbols that are vendor extensions are put in another, and each
+application program would have a package for its own symbols.
+Certain symbols are ``exported'' by a package and others are
+internal; certain packages ``use'' or import the exported symbols
+of other packages. To access symbols that would not normally be
+visible due to this importing and exporting, Common Lisp provides
+a syntax like @code{package:symbol} or @code{package::symbol}.
+
+Emacs Lisp has a single namespace for all interned symbols, and
+then uses a naming convention of putting a prefix like @code{cl-}
+in front of the name. Some Emacs packages adopt the Common Lisp-like
+convention of using @code{cl:} or @code{cl::} as the prefix.
+However, the Emacs parser does not understand colons and just
+treats them as part of the symbol name. Thus, while @code{mapcar}
+and @code{lisp:mapcar} may refer to the same symbol in Common
+Lisp, they are totally distinct in Emacs Lisp. Common Lisp
+programs that refer to a symbol by the full name sometimes
+and the short name other times will not port cleanly to Emacs.
+
+Emacs Lisp does have a concept of ``obarrays'', which are
+package-like collections of symbols, but this feature is not
+strong enough to be used as a true package mechanism.
+
+@item
+The @code{format} function is quite different between Common
+Lisp and Emacs Lisp. It takes an additional ``destination''
+argument before the format string. A destination of @code{nil}
+means to format to a string as in Emacs Lisp; a destination
+of @code{t} means to write to the terminal (similar to
+@code{message} in Emacs). Also, format control strings are
+utterly different; @code{~} is used instead of @code{%} to
+introduce format codes, and the set of available codes is
+much richer. There are no notations like @code{\n} for
+string literals; instead, @code{format} is used with the
+``newline'' format code, @code{~%}. More advanced formatting
+codes provide such features as paragraph filling, case
+conversion, and even loops and conditionals.
+
+While it would have been possible to implement most of Common
+Lisp @code{format} in this package (under the name @code{cl-format},
+of course), it was not deemed worthwhile. It would have required
+a huge amount of code to implement even a decent subset of
+@code{format}, yet the functionality it would provide over
+Emacs Lisp's @code{format} would rarely be useful.
+
+@item
+Vector constants use square brackets in Emacs Lisp, but
+@code{#(a b c)} notation in Common Lisp. To further complicate
+matters, Emacs has its own @code{#(} notation for
+something entirely different---strings with properties.
+
+@item
+Characters are distinct from integers in Common Lisp. The notation
+for character constants is also different: @code{#\A} in Common Lisp
+where Emacs Lisp uses @code{?A}. Also, @code{string=} and
+@code{string-equal} are synonyms in Emacs Lisp, whereas the latter is
+case-insensitive in Common Lisp.
+
+@item
+Data types. Some Common Lisp data types do not exist in Emacs
+Lisp. Rational numbers and complex numbers are not present,
+nor are large integers (all integers are ``fixnums''). All
+arrays are one-dimensional. There are no readtables or pathnames;
+streams are a set of existing data types rather than a new data
+type of their own. Hash tables, random-states, structures, and
+packages (obarrays) are built from Lisp vectors or lists rather
+than being distinct types.
+
+@item
+The Common Lisp Object System (CLOS) is not implemented,
+nor is the Common Lisp Condition System. However, the EIEIO package
+(@pxref{Top, , Introduction, eieio, EIEIO}) does implement some
+CLOS functionality.
+
+@item
+Common Lisp features that are completely redundant with Emacs
+Lisp features of a different name generally have not been
+implemented. For example, Common Lisp writes @code{defconstant}
+where Emacs Lisp uses @code{defconst}. Similarly, @code{make-list}
+takes its arguments in different ways in the two Lisps but does
+exactly the same thing, so this package has not bothered to
+implement a Common Lisp-style @code{make-list}.
+
+@item
+A few more notable Common Lisp features not included in this
+package: @code{compiler-let}, @code{tagbody}, @code{prog},
+@code{ldb/dpb}, @code{parse-integer}, @code{cerror}.
+
+@item
+Recursion. While recursion works in Emacs Lisp just like it
+does in Common Lisp, various details of the Emacs Lisp system
+and compiler make recursion much less efficient than it is in
+most Lisps. Some schools of thought prefer to use recursion
+in Lisp over other techniques; they would sum a list of
+numbers using something like
@example
-(cl-assert (> x 10) t "x is too small: %d")
+(defun sum-list (list)
+ (if list
+ (+ (car list) (sum-list (cdr list)))
+ 0))
@end example
-This usage of @var{show-args} is an extension to Common Lisp. In
-true Common Lisp, the second argument gives a list of @var{places}
-which can be @code{setf}'d by the user before continuing from the
-error. Since Emacs Lisp does not support continuable errors, it
-makes no sense to specify @var{places}.
-@end defspec
-
-@defspec cl-check-type form type [string]
-This form verifies that @var{form} evaluates to a value of type
-@var{type}. If so, it returns @code{nil}. If not, @code{cl-check-type}
-signals a @code{wrong-type-argument} error. The default error message
-lists the erroneous value along with @var{type} and @var{form}
-themselves. If @var{string} is specified, it is included in the
-error message in place of @var{type}. For example:
+@noindent
+where a more iteratively-minded programmer might write one of
+these forms:
@example
-(cl-check-type x (integer 1 *) "a positive integer")
+(let ((total 0)) (dolist (x my-list) (incf total x)) total)
+(loop for x in my-list sum x)
@end example
-@xref{Type Predicates}, for a description of the type specifiers
-that may be used for @var{type}.
+While this would be mainly a stylistic choice in most Common Lisps,
+in Emacs Lisp you should be aware that the iterative forms are
+much faster than recursion. Also, Lisp programmers will want to
+note that the current Emacs Lisp compiler does not optimize tail
+recursion.
+@end itemize
-Note that in Common Lisp, the first argument to @code{check-type}
-must be a @var{place} suitable for use by @code{setf}, because
-@code{check-type} signals a continuable error that allows the
-user to modify @var{place}.
-@end defspec
+@node Obsolete Features
+@appendix Obsolete Features
-@node Efficiency Concerns
-@appendix Efficiency Concerns
+This section describes some features of the package that are obsolete
+and should not be used in new code. They are either only provided by
+the old @file{cl.el} entry point, not by the newer @file{cl-lib.el};
+or where versions with a @samp{cl-} prefix do exist they do not behave
+in exactly the same way.
-@appendixsec Macros
+@menu
+* Obsolete Lexical Binding:: An approximation of lexical binding.
+* Obsolete Macros:: Obsolete macros.
+* Obsolete Setf Customization:: Obsolete ways to customize setf.
+@end menu
-@noindent
-Many of the advanced features of this package, such as @code{cl-defun},
-@code{cl-loop}, etc., are implemented as Lisp macros. In
-byte-compiled code, these complex notations will be expanded into
-equivalent Lisp code which is simple and efficient. For example,
-the form
+@node Obsolete Lexical Binding
+@appendixsec Obsolete Lexical Binding
-@example
-(cl-incf i n)
-@end example
+The following macros are extensions to Common Lisp, where all bindings
+are lexical unless declared otherwise. These features are likewise
+obsolete since the introduction of true lexical binding in Emacs 24.1.
+@defmac lexical-let (bindings@dots{}) forms@dots{}
+This form is exactly like @code{let} except that the bindings it
+establishes are purely lexical.
+@end defmac
+
+@c FIXME remove this and refer to elisp manual.
+@c Maybe merge some stuff from here to there?
@noindent
-is expanded at compile-time to the Lisp form
+Lexical bindings are similar to local variables in a language like C:
+Only the code physically within the body of the @code{lexical-let}
+(after macro expansion) may refer to the bound variables.
@example
-(setq i (+ i n))
+(setq a 5)
+(defun foo (b) (+ a b))
+(let ((a 2)) (foo a))
+ @result{} 4
+(lexical-let ((a 2)) (foo a))
+ @result{} 7
@end example
@noindent
-which is the most efficient ways of doing this operation
-in Lisp. Thus, there is no performance penalty for using the more
-readable @code{cl-incf} form in your compiled code.
+In this example, a regular @code{let} binding of @code{a} actually
+makes a temporary change to the global variable @code{a}, so @code{foo}
+is able to see the binding of @code{a} to 2. But @code{lexical-let}
+actually creates a distinct local variable @code{a} for use within its
+body, without any effect on the global variable of the same name.
-@emph{Interpreted} code, on the other hand, must expand these macros
-every time they are executed. For this reason it is strongly
-recommended that code making heavy use of macros be compiled.
-@c FIXME why are they not labelled as macros?
-(The features labeled ``Special Form'' instead of ``Function'' in
-this manual are macros.) A loop using @code{cl-incf} a hundred times
-will execute considerably faster if compiled, and will also
-garbage-collect less because the macro expansion will not have
-to be generated, used, and thrown away a hundred times.
+The most important use of lexical bindings is to create @dfn{closures}.
+A closure is a function object that refers to an outside lexical
+variable (@pxref{Closures,,,elisp,GNU Emacs Lisp Reference Manual}).
+For example:
-You can find out how a macro expands by using the
-@code{cl-prettyexpand} function.
+@example
+(defun make-adder (n)
+ (lexical-let ((n n))
+ (function (lambda (m) (+ n m)))))
+(setq add17 (make-adder 17))
+(funcall add17 4)
+ @result{} 21
+@end example
-@defun cl-prettyexpand form &optional full
-This function takes a single Lisp form as an argument and inserts
-a nicely formatted copy of it in the current buffer (which must be
-in Lisp mode so that indentation works properly). It also expands
-all Lisp macros which appear in the form. The easiest way to use
-this function is to go to the @file{*scratch*} buffer and type, say,
+@noindent
+The call @code{(make-adder 17)} returns a function object which adds
+17 to its argument. If @code{let} had been used instead of
+@code{lexical-let}, the function object would have referred to the
+global @code{n}, which would have been bound to 17 only during the
+call to @code{make-adder} itself.
@example
-(cl-prettyexpand '(cl-loop for x below 10 collect x))
+(defun make-counter ()
+ (lexical-let ((n 0))
+ (cl-function (lambda (&optional (m 1)) (cl-incf n m)))))
+(setq count-1 (make-counter))
+(funcall count-1 3)
+ @result{} 3
+(funcall count-1 14)
+ @result{} 17
+(setq count-2 (make-counter))
+(funcall count-2 5)
+ @result{} 5
+(funcall count-1 2)
+ @result{} 19
+(funcall count-2)
+ @result{} 6
@end example
@noindent
-and type @kbd{C-x C-e} immediately after the closing parenthesis;
-the expansion
+Here we see that each call to @code{make-counter} creates a distinct
+local variable @code{n}, which serves as a private counter for the
+function object that is returned.
+
+Closed-over lexical variables persist until the last reference to
+them goes away, just like all other Lisp objects. For example,
+@code{count-2} refers to a function object which refers to an
+instance of the variable @code{n}; this is the only reference
+to that variable, so after @code{(setq count-2 nil)} the garbage
+collector would be able to delete this instance of @code{n}.
+Of course, if a @code{lexical-let} does not actually create any
+closures, then the lexical variables are free as soon as the
+@code{lexical-let} returns.
+
+Many closures are used only during the extent of the bindings they
+refer to; these are known as ``downward funargs'' in Lisp parlance.
+When a closure is used in this way, regular Emacs Lisp dynamic
+bindings suffice and will be more efficient than @code{lexical-let}
+closures:
@example
-(cl-block nil
- (let* ((x 0)
- (G1004 nil))
- (while (< x 10)
- (setq G1004 (cons x G1004))
- (setq x (+ x 1)))
- (nreverse G1004)))
+(defun add-to-list (x list)
+ (mapcar (lambda (y) (+ x y))) list)
+(add-to-list 7 '(1 2 5))
+ @result{} (8 9 12)
@end example
@noindent
-will be inserted into the buffer. (The @code{cl-block} macro is
-expanded differently in the interpreter and compiler, so
-@code{cl-prettyexpand} just leaves it alone. The temporary
-variable @code{G1004} was created by @code{cl-gensym}.)
+Since this lambda is only used while @code{x} is still bound,
+it is not necessary to make a true closure out of it.
-If the optional argument @var{full} is true, then @emph{all}
-macros are expanded, including @code{cl-block}, @code{cl-eval-when},
-and compiler macros. Expansion is done as if @var{form} were
-a top-level form in a file being compiled. For example,
+You can use @code{defun} or @code{flet} inside a @code{lexical-let}
+to create a named closure. If several closures are created in the
+body of a single @code{lexical-let}, they all close over the same
+instance of the lexical variable.
+
+@defmac lexical-let* (bindings@dots{}) forms@dots{}
+This form is just like @code{lexical-let}, except that the bindings
+are made sequentially in the manner of @code{let*}.
+@end defmac
+
+@node Obsolete Macros
+@appendixsec Obsolete Macros
+
+The following macros are obsolete, and are replaced by versions with
+a @samp{cl-} prefix that do not behave in exactly the same way.
+Consequently, the @file{cl.el} versions are not simply aliases to the
+@file{cl-lib.el} versions.
+
+@defmac flet (bindings@dots{}) forms@dots{}
+This macro is replaced by @code{cl-flet} (@pxref{Function Bindings}),
+which behaves the same way as Common Lisp's @code{flet}.
+This @code{flet} takes the same arguments as @code{cl-flet}, but does
+not behave in precisely the same way.
+
+While @code{flet} in Common Lisp establishes a lexical function
+binding, this @code{flet} makes a dynamic binding (it dates from a
+time before Emacs had lexical binding). The result is
+that @code{flet} affects indirect calls to a function as well as calls
+directly inside the @code{flet} form itself.
+
+This will even work on Emacs primitives, although note that some calls
+to primitive functions internal to Emacs are made without going
+through the symbol's function cell, and so will not be affected by
+@code{flet}. For example,
@example
-(cl-prettyexpand '(cl-pushnew 'x list))
- @print{} (setq list (cl-adjoin 'x list))
-(cl-prettyexpand '(cl-pushnew 'x list) t)
- @print{} (setq list (if (memq 'x list) list (cons 'x list)))
-(cl-prettyexpand '(caddr (cl-member 'a list)) t)
- @print{} (car (cdr (cdr (memq 'a list))))
+(flet ((message (&rest args) (push args saved-msgs)))
+ (do-something))
@end example
-Note that @code{cl-adjoin}, @code{cl-caddr}, and @code{cl-member} all
-have built-in compiler macros to optimize them in common cases.
-@end defun
+This code attempts to replace the built-in function @code{message}
+with a function that simply saves the messages in a list rather
+than displaying them. The original definition of @code{message}
+will be restored after @code{do-something} exits. This code will
+work fine on messages generated by other Lisp code, but messages
+generated directly inside Emacs will not be caught since they make
+direct C-language calls to the message routines rather than going
+through the Lisp @code{message} function.
-@ifinfo
-@example
+@c Bug#411.
+Note that many primitives (e.g., @code{+}) have special byte-compile
+handling. Attempts to redefine such functions using @code{flet} will
+fail if byte-compiled.
+@c Or cl-flet.
+@c In such cases, use @code{labels} instead.
+@end defmac
+
+@defmac labels (bindings@dots{}) forms@dots{}
+This macro is replaced by @code{cl-labels} (@pxref{Function Bindings}),
+which behaves the same way as Common Lisp's @code{labels}.
+This @code{labels} takes the same arguments as @code{cl-labels}, but
+does not behave in precisely the same way.
+
+This version of @code{labels} uses the obsolete @code{lexical-let}
+form (@pxref{Obsolete Lexical Binding}), rather than the true
+lexical binding that @code{cl-labels} uses.
+@end defmac
+
+@defmac letf (bindings@dots{}) forms@dots{}
+This macro is almost exactly the same as @code{cl-letf}, which
+replaces it (@pxref{Modify Macros}). The only difference is in
+details that relate to some deprecated usage of @code{symbol-function}
+in place forms.
+@end defmac
+
+@node Obsolete Setf Customization
+@appendixsec Obsolete Ways to Customize Setf
-@end example
-@end ifinfo
-@appendixsec Error Checking
+Common Lisp defines three macros, @code{define-modify-macro},
+@code{defsetf}, and @code{define-setf-method}, that allow the
+user to extend generalized variables in various ways.
+In Emacs, these are obsolete, replaced by various features of
+@file{gv.el} in Emacs 24.3.
+@xref{Adding Generalized Variables,,,elisp,GNU Emacs Lisp Reference Manual}.
-@noindent
-Common Lisp compliance has in general not been sacrificed for the
-sake of efficiency. A few exceptions have been made for cases
-where substantial gains were possible at the expense of marginal
-incompatibility.
-The Common Lisp standard (as embodied in Steele's book) uses the
-phrase ``it is an error if'' to indicate a situation which is not
-supposed to arise in complying programs; implementations are strongly
-encouraged but not required to signal an error in these situations.
-This package sometimes omits such error checking in the interest of
-compactness and efficiency. For example, @code{cl-do} variable
-specifiers are supposed to be lists of one, two, or three forms;
-extra forms are ignored by this package rather than signaling a
-syntax error. The @code{cl-endp} function is simply a synonym for
-@code{null} in this package. Functions taking keyword arguments
-will accept an odd number of arguments, treating the trailing
-keyword as if it were followed by the value @code{nil}.
+@defmac define-modify-macro name arglist function [doc-string]
+This macro defines a ``read-modify-write'' macro similar to
+@code{cl-incf} and @code{cl-decf}. You can replace this macro
+with @code{gv-letplace}.
-Argument lists (as processed by @code{cl-defun} and friends)
-@emph{are} checked rigorously except for the minor point just
-mentioned; in particular, keyword arguments are checked for
-validity, and @code{&allow-other-keys} and @code{:allow-other-keys}
-are fully implemented. Keyword validity checking is slightly
-time consuming (though not too bad in byte-compiled code);
-you can use @code{&allow-other-keys} to omit this check. Functions
-defined in this package such as @code{cl-find} and @code{cl-member}
-do check their keyword arguments for validity.
+The macro @var{name} is defined to take a @var{place} argument
+followed by additional arguments described by @var{arglist}. The call
-@ifinfo
@example
-
+(@var{name} @var{place} @var{args}@dots{})
@end example
-@end ifinfo
-@appendixsec Optimizing Compiler
@noindent
-Use of the optimizing Emacs compiler is highly recommended; many of the Common
-Lisp macros emit
-code which can be improved by optimization. In particular,
-@code{cl-block}s (whether explicit or implicit in constructs like
-@code{cl-defun} and @code{cl-loop}) carry a fair run-time penalty; the
-optimizing compiler removes @code{cl-block}s which are not actually
-referenced by @code{cl-return} or @code{cl-return-from} inside the block.
+will be expanded to
-@node Common Lisp Compatibility
-@appendix Common Lisp Compatibility
+@example
+(cl-callf @var{func} @var{place} @var{args}@dots{})
+@end example
@noindent
-Following is a list of all known incompatibilities between this
-package and Common Lisp as documented in Steele (2nd edition).
-
-@ignore
-Certain function names, such as @code{member}, @code{assoc}, and
-@code{floor}, were already taken by (incompatible) Emacs Lisp
-functions; this package appends @samp{*} to the names of its
-Common Lisp versions of these functions.
-@end ignore
-
-The word @code{cl-defun} is required instead of @code{defun} in order
-to use extended Common Lisp argument lists in a function. Likewise,
-@code{cl-defmacro} and @code{cl-function} are versions of those forms
-which understand full-featured argument lists. The @code{&whole}
-keyword does not work in @code{defmacro} argument lists (except
-inside recursive argument lists).
-
-The @code{equal} predicate does not distinguish
-between IEEE floating-point plus and minus zero. The @code{cl-equalp}
-predicate has several differences with Common Lisp; @pxref{Predicates}.
+which in turn is roughly equivalent to
-The @code{setf} mechanism is entirely compatible, except that
-setf-methods return a list of five values rather than five
-values directly. Also, the new ``@code{setf} function'' concept
-(typified by @code{(defun (setf foo) @dots{})}) is not implemented.
+@example
+(setf @var{place} (@var{func} @var{place} @var{args}@dots{}))
+@end example
-The @code{cl-do-all-symbols} form is the same as @code{cl-do-symbols}
-with no @var{obarray} argument. In Common Lisp, this form would
-iterate over all symbols in all packages. Since Emacs obarrays
-are not a first-class package mechanism, there is no way for
-@code{cl-do-all-symbols} to locate any but the default obarray.
+For example:
-The @code{cl-loop} macro is complete except that @code{loop-finish}
-and type specifiers are unimplemented.
+@example
+(define-modify-macro incf (&optional (n 1)) +)
+(define-modify-macro concatf (&rest args) concat)
+@end example
-The multiple-value return facility treats lists as multiple
-values, since Emacs Lisp cannot support multiple return values
-directly. The macros will be compatible with Common Lisp if
-@code{values} or @code{values-list} is always used to return to
-a @code{cl-multiple-value-bind} or other multiple-value receiver;
-if @code{values} is used without @code{cl-multiple-value-@dots{}}
-or vice-versa the effect will be different from Common Lisp.
+Note that @code{&key} is not allowed in @var{arglist}, but
+@code{&rest} is sufficient to pass keywords on to the function.
-Many Common Lisp declarations are ignored, and others match
-the Common Lisp standard in concept but not in detail. For
-example, local @code{special} declarations, which are purely
-advisory in Emacs Lisp, do not rigorously obey the scoping rules
-set down in Steele's book.
+Most of the modify macros defined by Common Lisp do not exactly
+follow the pattern of @code{define-modify-macro}. For example,
+@code{push} takes its arguments in the wrong order, and @code{pop}
+is completely irregular.
-The variable @code{cl--gensym-counter} starts out with a pseudo-random
-value rather than with zero. This is to cope with the fact that
-generated symbols become interned when they are written to and
-loaded back from a file.
+The above @code{incf} example could be written using
+@code{gv-letplace} as:
+@example
+(defmacro incf (place &optional n)
+ (gv-letplace (getter setter) place
+ (macroexp-let2 nil v (or n 1)
+ (funcall setter `(+ ,v ,getter)))))
+@end example
+@ignore
+(defmacro concatf (place &rest args)
+ (gv-letplace (getter setter) place
+ (macroexp-let2 nil v (mapconcat 'identity args "")
+ (funcall setter `(concat ,getter ,v)))))
+@end ignore
+@end defmac
-The @code{cl-defstruct} facility is compatible, except that structures
-are of type @code{:type vector :named} by default rather than some
-special, distinct type. Also, the @code{:type} slot option is ignored.
+@defmac defsetf access-fn update-fn
+This is the simpler of two @code{defsetf} forms, and is
+replaced by @code{gv-define-simple-setter}.
-The second argument of @code{cl-check-type} is treated differently.
+With @var{access-fn} the name of a function that accesses a place,
+this declares @var{update-fn} to be the corresponding store function.
+From now on,
-@node Porting Common Lisp
-@appendix Porting Common Lisp
+@example
+(setf (@var{access-fn} @var{arg1} @var{arg2} @var{arg3}) @var{value})
+@end example
@noindent
-This package is meant to be used as an extension to Emacs Lisp,
-not as an Emacs implementation of true Common Lisp. Some of the
-remaining differences between Emacs Lisp and Common Lisp make it
-difficult to port large Common Lisp applications to Emacs. For
-one, some of the features in this package are not fully compliant
-with ANSI or Steele; @pxref{Common Lisp Compatibility}. But there
-are also quite a few features that this package does not provide
-at all. Here are some major omissions that you will want to watch out
-for when bringing Common Lisp code into Emacs.
+will be expanded to
-@itemize @bullet
-@item
-Case-insensitivity. Symbols in Common Lisp are case-insensitive
-by default. Some programs refer to a function or variable as
-@code{foo} in one place and @code{Foo} or @code{FOO} in another.
-Emacs Lisp will treat these as three distinct symbols.
+@example
+(@var{update-fn} @var{arg1} @var{arg2} @var{arg3} @var{value})
+@end example
-Some Common Lisp code is written entirely in upper case. While Emacs
-is happy to let the program's own functions and variables use
-this convention, calls to Lisp builtins like @code{if} and
-@code{defun} will have to be changed to lower case.
+@noindent
+The @var{update-fn} is required to be either a true function, or
+a macro that evaluates its arguments in a function-like way. Also,
+the @var{update-fn} is expected to return @var{value} as its result.
+Otherwise, the above expansion would not obey the rules for the way
+@code{setf} is supposed to behave.
-@item
-Lexical scoping. In Common Lisp, function arguments and @code{let}
-bindings apply only to references physically within their bodies
-(or within macro expansions in their bodies). Emacs Lisp, by
-contrast, uses @dfn{dynamic scoping} wherein a binding to a
-variable is visible even inside functions called from the body.
+As a special (non-Common-Lisp) extension, a third argument of @code{t}
+to @code{defsetf} says that the return value of @code{update-fn} is
+not suitable, so that the above @code{setf} should be expanded to
+something more like
-Variables in Common Lisp can be made dynamically scoped by
-declaring them @code{special} or using @code{defvar}. In Emacs
-Lisp it is as if all variables were declared @code{special}.
+@example
+(let ((temp @var{value}))
+ (@var{update-fn} @var{arg1} @var{arg2} @var{arg3} temp)
+ temp)
+@end example
-Often you can use code that was written for lexical scoping
-even in a dynamically scoped Lisp, but not always. Here is
-an example of a Common Lisp code fragment that would fail in
-Emacs Lisp:
+Some examples are:
@example
-(defun map-odd-elements (func list)
- (loop for x in list
- for flag = t then (not flag)
- collect (if flag x (funcall func x))))
+(defsetf car setcar)
+(defsetf buffer-name rename-buffer t)
+@end example
-(defun add-odd-elements (list x)
- (map-odd-elements (lambda (a) (+ a x)) list))
+These translate directly to @code{gv-define-simple-setter}:
+
+@example
+(gv-define-simple-setter car setcar)
+(gv-define-simple-setter buffer-name rename-buffer t)
@end example
+@end defmac
-@noindent
-In Common Lisp, the two functions' usages of @code{x} are completely
-independent. In Emacs Lisp, the binding to @code{x} made by
-@code{add-odd-elements} will have been hidden by the binding
-in @code{map-odd-elements} by the time the @code{(+ a x)} function
-is called.
+@defmac defsetf access-fn arglist (store-var) forms@dots{}
+This is the second, more complex, form of @code{defsetf}.
+It can be replaced by @code{gv-define-setter}.
-(This package avoids such problems in its own mapping functions
-by using names like @code{cl--x} instead of @code{x} internally;
-as long as you don't use this prefix for your own
-variables no collision can occur.)
+This form of @code{defsetf} is rather like @code{defmacro} except for
+the additional @var{store-var} argument. The @var{forms} should
+return a Lisp form that stores the value of @var{store-var} into the
+generalized variable formed by a call to @var{access-fn} with
+arguments described by @var{arglist}. The @var{forms} may begin with
+a string which documents the @code{setf} method (analogous to the doc
+string that appears at the front of a function).
-@xref{Lexical Bindings}, for a description of the @code{lexical-let}
-form which establishes a Common Lisp-style lexical binding, and some
-examples of how it differs from Emacs's regular @code{let}.
+For example, the simple form of @code{defsetf} is shorthand for
-@item
-Reader macros. Common Lisp includes a second type of macro that
-works at the level of individual characters. For example, Common
-Lisp implements the quote notation by a reader macro called @code{'},
-whereas Emacs Lisp's parser just treats quote as a special case.
-Some Lisp packages use reader macros to create special syntaxes
-for themselves, which the Emacs parser is incapable of reading.
+@example
+(defsetf @var{access-fn} (&rest args) (store)
+ (append '(@var{update-fn}) args (list store)))
+@end example
-@item
-Other syntactic features. Common Lisp provides a number of
-notations beginning with @code{#} that the Emacs Lisp parser
-won't understand. For example, @samp{#| ... |#} is an
-alternate comment notation, and @samp{#+lucid (foo)} tells
-the parser to ignore the @code{(foo)} except in Lucid Common
-Lisp.
+The Lisp form that is returned can access the arguments from
+@var{arglist} and @var{store-var} in an unrestricted fashion;
+macros like @code{cl-incf} that invoke this
+setf-method will insert temporary variables as needed to make
+sure the apparent order of evaluation is preserved.
-@item
-Packages. In Common Lisp, symbols are divided into @dfn{packages}.
-Symbols that are Lisp built-ins are typically stored in one package;
-symbols that are vendor extensions are put in another, and each
-application program would have a package for its own symbols.
-Certain symbols are ``exported'' by a package and others are
-internal; certain packages ``use'' or import the exported symbols
-of other packages. To access symbols that would not normally be
-visible due to this importing and exporting, Common Lisp provides
-a syntax like @code{package:symbol} or @code{package::symbol}.
+Another standard example:
-Emacs Lisp has a single namespace for all interned symbols, and
-then uses a naming convention of putting a prefix like @code{cl-}
-in front of the name. Some Emacs packages adopt the Common Lisp-like
-convention of using @code{cl:} or @code{cl::} as the prefix.
-However, the Emacs parser does not understand colons and just
-treats them as part of the symbol name. Thus, while @code{mapcar}
-and @code{lisp:mapcar} may refer to the same symbol in Common
-Lisp, they are totally distinct in Emacs Lisp. Common Lisp
-programs which refer to a symbol by the full name sometimes
-and the short name other times will not port cleanly to Emacs.
+@example
+(defsetf nth (n x) (store)
+ `(setcar (nthcdr ,n ,x) ,store))
+@end example
-Emacs Lisp does have a concept of ``obarrays'', which are
-package-like collections of symbols, but this feature is not
-strong enough to be used as a true package mechanism.
+You could write this using @code{gv-define-setter} as:
-@item
-The @code{format} function is quite different between Common
-Lisp and Emacs Lisp. It takes an additional ``destination''
-argument before the format string. A destination of @code{nil}
-means to format to a string as in Emacs Lisp; a destination
-of @code{t} means to write to the terminal (similar to
-@code{message} in Emacs). Also, format control strings are
-utterly different; @code{~} is used instead of @code{%} to
-introduce format codes, and the set of available codes is
-much richer. There are no notations like @code{\n} for
-string literals; instead, @code{format} is used with the
-``newline'' format code, @code{~%}. More advanced formatting
-codes provide such features as paragraph filling, case
-conversion, and even loops and conditionals.
+@example
+(gv-define-setter nth (store n x)
+ `(setcar (nthcdr ,n ,x) ,store))
+@end example
+@end defmac
-While it would have been possible to implement most of Common
-Lisp @code{format} in this package (under the name @code{cl-format},
-of course), it was not deemed worthwhile. It would have required
-a huge amount of code to implement even a decent subset of
-@code{cl-format}, yet the functionality it would provide over
-Emacs Lisp's @code{format} would rarely be useful.
+@defmac define-setf-method access-fn arglist forms@dots{}
+This is the most general way to create new place forms. You can
+replace this by @code{gv-define-setter} or @code{gv-define-expander}.
-@item
-Vector constants use square brackets in Emacs Lisp, but
-@code{#(a b c)} notation in Common Lisp. To further complicate
-matters, Emacs has its own @code{#(} notation for
-something entirely different---strings with properties.
+When a @code{setf} to @var{access-fn} with arguments described by
+@var{arglist} is expanded, the @var{forms} are evaluated and must
+return a list of five items:
+@enumerate
@item
-Characters are distinct from integers in Common Lisp. The notation
-for character constants is also different: @code{#\A} in Common Lisp
-where Emacs Lisp uses @code{?A}. Also, @code{string=} and
-@code{string-equal} are synonyms in Emacs Lisp, whereas the latter is
-case-insensitive in Common Lisp.
+A list of @dfn{temporary variables}.
@item
-Data types. Some Common Lisp data types do not exist in Emacs
-Lisp. Rational numbers and complex numbers are not present,
-nor are large integers (all integers are ``fixnums''). All
-arrays are one-dimensional. There are no readtables or pathnames;
-streams are a set of existing data types rather than a new data
-type of their own. Hash tables, random-states, structures, and
-packages (obarrays) are built from Lisp vectors or lists rather
-than being distinct types.
+A list of @dfn{value forms} corresponding to the temporary variables
+above. The temporary variables will be bound to these value forms
+as the first step of any operation on the generalized variable.
@item
-The Common Lisp Object System (CLOS) is not implemented,
-nor is the Common Lisp Condition System. However, the EIEIO package
-(@pxref{Top, , Introduction, eieio, EIEIO}) does implement some
-CLOS functionality.
+A list of exactly one @dfn{store variable} (generally obtained
+from a call to @code{gensym}).
@item
-Common Lisp features that are completely redundant with Emacs
-Lisp features of a different name generally have not been
-implemented. For example, Common Lisp writes @code{defconstant}
-where Emacs Lisp uses @code{defconst}. Similarly, @code{make-list}
-takes its arguments in different ways in the two Lisps but does
-exactly the same thing, so this package has not bothered to
-implement a Common Lisp-style @code{make-list}.
+A Lisp form that stores the contents of the store variable into
+the generalized variable, assuming the temporaries have been
+bound as described above.
@item
-A few more notable Common Lisp features not included in this
-package: @code{compiler-let}, @code{tagbody}, @code{prog},
-@code{ldb/dpb}, @code{parse-integer}, @code{cerror}.
+A Lisp form that accesses the contents of the generalized variable,
+assuming the temporaries have been bound.
+@end enumerate
-@item
-Recursion. While recursion works in Emacs Lisp just like it
-does in Common Lisp, various details of the Emacs Lisp system
-and compiler make recursion much less efficient than it is in
-most Lisps. Some schools of thought prefer to use recursion
-in Lisp over other techniques; they would sum a list of
-numbers using something like
+This is exactly like the Common Lisp macro of the same name,
+except that the method returns a list of five values rather
+than the five values themselves, since Emacs Lisp does not
+support Common Lisp's notion of multiple return values.
+(Note that the @code{setf} implementation provided by @file{gv.el}
+does not use this five item format. Its use here is only for
+backwards compatibility.)
-@example
-(defun sum-list (list)
- (if list
- (+ (car list) (sum-list (cdr list)))
- 0))
-@end example
+Once again, the @var{forms} may begin with a documentation string.
-@noindent
-where a more iteratively-minded programmer might write one of
-these forms:
+A setf-method should be maximally conservative with regard to
+temporary variables. In the setf-methods generated by
+@code{defsetf}, the second return value is simply the list of
+arguments in the place form, and the first return value is a
+list of a corresponding number of temporary variables generated
+@c FIXME I don't think this is true anymore.
+by @code{cl-gensym}. Macros like @code{cl-incf} that
+use this setf-method will optimize away most temporaries that
+turn out to be unnecessary, so there is little reason for the
+setf-method itself to optimize.
+@end defmac
-@example
-(let ((total 0)) (dolist (x my-list) (cl-incf total x)) total)
-(cl-loop for x in my-list sum x)
-@end example
+@c Removed in Emacs 24.3, not possible to make a compatible replacement.
+@ignore
+@defun get-setf-method place &optional env
+This function returns the setf-method for @var{place}, by
+invoking the definition previously recorded by @code{defsetf}
+or @code{define-setf-method}. The result is a list of five
+values as described above. You can use this function to build
+your own @code{cl-incf}-like modify macros.
+
+The argument @var{env} specifies the ``environment'' to be
+passed on to @code{macroexpand} if @code{get-setf-method} should
+need to expand a macro in @var{place}. It should come from
+an @code{&environment} argument to the macro or setf-method
+that called @code{get-setf-method}.
+@end defun
+@end ignore
-While this would be mainly a stylistic choice in most Common Lisps,
-in Emacs Lisp you should be aware that the iterative forms are
-much faster than recursion. Also, Lisp programmers will want to
-note that the current Emacs Lisp compiler does not optimize tail
-recursion.
-@end itemize
@node GNU Free Documentation License
@appendix GNU Free Documentation License
@printindex vr
@bye
-
HCoop / bpt / emacs.git / blobdiff