@c -*-texinfo-*-
@c This is part of the GNU Guile Reference Manual.
-@c Copyright (C) 1996, 1997, 2000, 2001, 2002, 2003, 2004
+@c Copyright (C) 1996, 1997, 2000, 2001, 2002, 2003, 2004, 2006, 2007, 2008, 2009, 2010, 2011
@c Free Software Foundation, Inc.
@c See the file guile.texi for copying conditions.
-@page
@node SRFI Support
@section SRFI Support Modules
@cindex SRFI
over the available SRFIs and some usage hints. For complete
documentation, design rationales and further examples, we advise you to
get the relevant SRFI documents from the SRFI home page
-@url{http://srfi.schemers.org}.
+@url{http://srfi.schemers.org/}.
@menu
* About SRFI Usage:: What to know about Guile's SRFI support.
* SRFI-8:: receive.
* SRFI-9:: define-record-type.
* SRFI-10:: Hash-Comma Reader Extension.
-* SRFI-11:: let-values and let-values*.
+* SRFI-11:: let-values and let*-values.
* SRFI-13:: String library.
* SRFI-14:: Character-set library.
* SRFI-16:: case-lambda
* SRFI-17:: Generalized set!
+* SRFI-18:: Multithreading support
* SRFI-19:: Time/Date library.
+* SRFI-23:: Error reporting
* SRFI-26:: Specializing parameters
+* SRFI-27:: Sources of Random Bits
+* SRFI-30:: Nested multi-line block comments
* SRFI-31:: A special form `rec' for recursive evaluation
+* SRFI-34:: Exception handling.
+* SRFI-35:: Conditions.
+* SRFI-37:: args-fold program argument processor
+* SRFI-38:: External Representation for Data With Shared Structure
+* SRFI-39:: Parameter objects
+* SRFI-42:: Eager comprehensions
+* SRFI-45:: Primitives for expressing iterative lazy algorithms
+* SRFI-55:: Requiring Features.
+* SRFI-60:: Integers as bits.
+* SRFI-61:: A more general `cond' clause
+* SRFI-67:: Compare procedures
+* SRFI-69:: Basic hash tables.
+* SRFI-88:: Keyword objects.
+* SRFI-98:: Accessing environment variables.
@end menu
@end example
@end deffn
-The Guile core provides features @code{guile}, @code{r5rs},
-@code{srfi-0} and @code{srfi-6} initially. Other SRFI feature symbols
-are defined once their code has been loaded with @code{use-modules},
-since only then are their bindings available.
+@noindent
+The Guile core has the following features,
+
+@example
+guile
+guile-2 ;; starting from Guile 2.x
+r5rs
+srfi-0
+srfi-4
+srfi-6
+srfi-13
+srfi-14
+@end example
+
+Other SRFI feature symbols are defined once their code has been loaded
+with @code{use-modules}, since only then are their bindings available.
The @samp{--use-srfi} command line option (@pxref{Invoking Guile}) is
a good way to load SRFIs to satisfy @code{cond-expand} when running a
(use-modules (srfi srfi-8))))
@end example
+@cindex @code{guile-2} SRFI-0 feature
+@cindex portability between 2.0 and older versions
+Likewise, testing the @code{guile-2} feature allows code to be portable
+between Guile 2.0 and previous versions of Guile. For instance, it
+makes it possible to write code that accounts for Guile 2.0's compiler,
+yet be correctly interpreted on 1.8 and earlier versions:
+
+@example
+(cond-expand (guile-2 (eval-when (compile)
+ ;; This must be evaluated at compile time.
+ (fluid-set! current-reader my-reader)))
+ (guile
+ ;; Earlier versions of Guile do not have a
+ ;; separate compilation phase.
+ (fluid-set! current-reader my-reader)))
+@end example
+
It should be noted that @code{cond-expand} is separate from the
@code{*features*} mechanism (@pxref{Feature Tracking}), feature
symbols in one are unrelated to those in the other.
The procedures in this section test specific properties of lists.
@deffn {Scheme Procedure} proper-list? obj
-Return @code{#t} if @var{obj} is a proper list, that is a finite list,
-terminated with the empty list. Otherwise, return @code{#f}.
+Return @code{#t} if @var{obj} is a proper list, or @code{#f}
+otherwise. This is the same as the core @code{list?} (@pxref{List
+Predicates}).
+
+A proper list is a list which ends with the empty list @code{()} in
+the usual way. The empty list @code{()} itself is a proper list too.
+
+@example
+(proper-list? '(1 2 3)) @result{} #t
+(proper-list? '()) @result{} #t
+@end example
@end deffn
@deffn {Scheme Procedure} circular-list? obj
-Return @code{#t} if @var{obj} is a circular list, otherwise return
-@code{#f}.
+Return @code{#t} if @var{obj} is a circular list, or @code{#f}
+otherwise.
+
+A circular list is a list where at some point the @code{cdr} refers
+back to a previous pair in the list (either the start or some later
+point), so that following the @code{cdr}s takes you around in a
+circle, with no end.
+
+@example
+(define x (list 1 2 3 4))
+(set-cdr! (last-pair x) (cddr x))
+x @result{} (1 2 3 4 3 4 3 4 ...)
+(circular-list? x) @result{} #t
+@end example
@end deffn
@deffn {Scheme Procedure} dotted-list? obj
-Return @code{#t} if @var{obj} is a dotted list, return @code{#f}
-otherwise. A dotted list is a finite list which is not terminated by
-the empty list, but some other value.
+Return @code{#t} if @var{obj} is a dotted list, or @code{#f}
+otherwise.
+
+A dotted list is a list where the @code{cdr} of the last pair is not
+the empty list @code{()}. Any non-pair @var{obj} is also considered a
+dotted list, with length zero.
+
+@example
+(dotted-list? '(1 2 . 3)) @result{} #t
+(dotted-list? 99) @result{} #t
+@end example
@end deffn
+It will be noted that any Scheme object passes exactly one of the
+above three tests @code{proper-list?}, @code{circular-list?} and
+@code{dotted-list?}. Non-lists are @code{dotted-list?}, finite lists
+are either @code{proper-list?} or @code{dotted-list?}, and infinite
+lists are @code{circular-list?}.
+
+@sp 1
@deffn {Scheme Procedure} null-list? lst
Return @code{#t} if @var{lst} is the empty list @code{()}, @code{#f}
otherwise. If something else than a proper or circular list is passed
@end deffn
@deffn {Scheme Procedure} take-right lst i
-Return the a list containing the @var{i} last elements of @var{lst}.
+Return a list containing the @var{i} last elements of @var{lst}.
+The return shares a common tail with @var{lst}.
@end deffn
@deffn {Scheme Procedure} drop-right lst i
@deffnx {Scheme Procedure} drop-right! lst i
-Return the a list containing all but the @var{i} last elements of
+Return a list containing all but the @var{i} last elements of
@var{lst}.
-@code{drop-right!} may modify the structure of the argument list
-@var{lst} in order to produce the result.
+@code{drop-right} always returns a new list, even when @var{i} is
+zero. @code{drop-right!} may modify the structure of the argument
+list @var{lst} in order to produce the result.
@end deffn
@deffn {Scheme Procedure} split-at lst i
@deffn {Scheme Procedure} append-reverse rev-head tail
@deffnx {Scheme Procedure} append-reverse! rev-head tail
-Reverse @var{rev-head}, append @var{tail} and return the result. This
-is equivalent to @code{(append (reverse @var{rev-head}) @var{tail})},
-but more efficient.
+Reverse @var{rev-head}, append @var{tail} to it, and return the
+result. This is equivalent to @code{(append (reverse @var{rev-head})
+@var{tail})}, but its implementation is more efficient.
+
+@example
+(append-reverse '(1 2 3) '(4 5 6)) @result{} (3 2 1 4 5 6)
+@end example
@code{append-reverse!} may modify @var{rev-head} in order to produce
the result.
@c FIXME::martin: Review me!
-@deffn {Scheme Procedure} fold kons knil lst1 lst2 @dots{}
-Fold the procedure @var{kons} across all elements of @var{lst1},
-@var{lst2}, @dots{}. Produce the result of
+@deffn {Scheme Procedure} fold proc init lst1 @dots{} lstN
+@deffnx {Scheme Procedure} fold-right proc init lst1 @dots{} lstN
+Apply @var{proc} to the elements of @var{lst1} @dots{} @var{lstN} to
+build a result, and return that result.
-@code{(@var{kons} @var{en1} @var{en2} @dots{} (@var{kons} @var{e21}
-@var{e22} (@var{kons} @var{e11} @var{e12} @var{knil})))},
+Each @var{proc} call is @code{(@var{proc} @var{elem1} @dots{}
+@var{elemN} @var{previous})}, where @var{elem1} is from @var{lst1},
+through @var{elemN} from @var{lstN}. @var{previous} is the return
+from the previous call to @var{proc}, or the given @var{init} for the
+first call. If any list is empty, just @var{init} is returned.
-if @var{enm} are the elements of the lists @var{lst1}, @var{lst2},
-@dots{}.
-@end deffn
+@code{fold} works through the list elements from first to last. The
+following shows a list reversal and the calls it makes,
-@deffn {Scheme Procedure} fold-right kons knil lst1 lst2 @dots{}
-Similar to @code{fold}, but applies @var{kons} in right-to-left order
-to the list elements, that is:
+@example
+(fold cons '() '(1 2 3))
-@code{(@var{kons} @var{e11} @var{e12}(@var{kons} @var{e21}
-@var{e22} @dots{} (@var{kons} @var{en1} @var{en2} @var{knil})))},
-@end deffn
+(cons 1 '())
+(cons 2 '(1))
+(cons 3 '(2 1)
+@result{} (3 2 1)
+@end example
-@deffn {Scheme Procedure} pair-fold kons knil lst1 lst2 @dots{}
-Like @code{fold}, but apply @var{kons} to the pairs of the list
-instead of the list elements.
-@end deffn
+@code{fold-right} works through the list elements from last to first,
+ie.@: from the right. So for example the following finds the longest
+string, and the last among equal longest,
+
+@example
+(fold-right (lambda (str prev)
+ (if (> (string-length str) (string-length prev))
+ str
+ prev))
+ ""
+ '("x" "abc" "xyz" "jk"))
+@result{} "xyz"
+@end example
+
+If @var{lst1} through @var{lstN} have different lengths, @code{fold}
+stops when the end of the shortest is reached; @code{fold-right}
+commences at the last element of the shortest. Ie.@: elements past
+the length of the shortest are ignored in the other @var{lst}s. At
+least one @var{lst} must be non-circular.
+
+@code{fold} should be preferred over @code{fold-right} if the order of
+processing doesn't matter, or can be arranged either way, since
+@code{fold} is a little more efficient.
+
+The way @code{fold} builds a result from iterating is quite general,
+it can do more than other iterations like say @code{map} or
+@code{filter}. The following for example removes adjacent duplicate
+elements from a list,
+
+@example
+(define (delete-adjacent-duplicates lst)
+ (fold-right (lambda (elem ret)
+ (if (equal? elem (first ret))
+ ret
+ (cons elem ret)))
+ (list (last lst))
+ lst))
+(delete-adjacent-duplicates '(1 2 3 3 4 4 4 5))
+@result{} (1 2 3 4 5)
+@end example
-@deffn {Scheme Procedure} pair-fold-right kons knil lst1 lst2 @dots{}
-Like @code{fold-right}, but apply @var{kons} to the pairs of the list
-instead of the list elements.
+Clearly the same sort of thing can be done with a @code{for-each} and
+a variable in which to build the result, but a self-contained
+@var{proc} can be re-used in multiple contexts, where a
+@code{for-each} would have to be written out each time.
@end deffn
-@deffn {Scheme Procedure} reduce f ridentity lst
-@code{reduce} is a variant of @code{fold}. If @var{lst} is
-@code{()}, @var{ridentity} is returned. Otherwise, @code{(fold f (car
-@var{lst}) (cdr @var{lst}))} is returned.
+@deffn {Scheme Procedure} pair-fold proc init lst1 @dots{} lstN
+@deffnx {Scheme Procedure} pair-fold-right proc init lst1 @dots{} lstN
+The same as @code{fold} and @code{fold-right}, but apply @var{proc} to
+the pairs of the lists instead of the list elements.
@end deffn
-@deffn {Scheme Procedure} reduce-right f ridentity lst
-This is the @code{fold-right} variant of @code{reduce}.
+@deffn {Scheme Procedure} reduce proc default lst
+@deffnx {Scheme Procedure} reduce-right proc default lst
+@code{reduce} is a variant of @code{fold}, where the first call to
+@var{proc} is on two elements from @var{lst}, rather than one element
+and a given initial value.
+
+If @var{lst} is empty, @code{reduce} returns @var{default} (this is
+the only use for @var{default}). If @var{lst} has just one element
+then that's the return value. Otherwise @var{proc} is called on the
+elements of @var{lst}.
+
+Each @var{proc} call is @code{(@var{proc} @var{elem} @var{previous})},
+where @var{elem} is from @var{lst} (the second and subsequent elements
+of @var{lst}), and @var{previous} is the return from the previous call
+to @var{proc}. The first element of @var{lst} is the @var{previous}
+for the first call to @var{proc}.
+
+For example, the following adds a list of numbers, the calls made to
+@code{+} are shown. (Of course @code{+} accepts multiple arguments
+and can add a list directly, with @code{apply}.)
+
+@example
+(reduce + 0 '(5 6 7)) @result{} 18
+
+(+ 6 5) @result{} 11
+(+ 7 11) @result{} 18
+@end example
+
+@code{reduce} can be used instead of @code{fold} where the @var{init}
+value is an ``identity'', meaning a value which under @var{proc}
+doesn't change the result, in this case 0 is an identity since
+@code{(+ 5 0)} is just 5. @code{reduce} avoids that unnecessary call.
+
+@code{reduce-right} is a similar variation on @code{fold-right},
+working from the end (ie.@: the right) of @var{lst}. The last element
+of @var{lst} is the @var{previous} for the first call to @var{proc},
+and the @var{elem} values go from the second last.
+
+@code{reduce} should be preferred over @code{reduce-right} if the
+order of processing doesn't matter, or can be arranged either way,
+since @code{reduce} is a little more efficient.
@end deffn
@deffn {Scheme Procedure} unfold p f g seed [tail-gen]
Maps each seed value to the corresponding list element.
@item g
-Maps each seed value to next seed valu.
+Maps each seed value to next seed value.
@item seed
The state value for the unfold.
Maps each seed value to the corresponding list element.
@item g
-Maps each seed value to next seed valu.
+Maps each seed value to next seed value.
@item seed
The state value for the unfold.
@var{pred} are made, and the return is @code{#t}.
@end deffn
-@deffn {Scheme Procedure} list-index pred lst1 lst2 @dots{}
-Return the index of the leftmost element that satisfies @var{pred}.
+@deffn {Scheme Procedure} list-index pred lst1 @dots{} lstN
+Return the index of the first set of elements, one from each of
+@var{lst1}@dots{}@var{lstN}, which satisfies @var{pred}.
+
+@var{pred} is called as @code{(@var{pred} elem1 @dots{} elemN)}.
+Searching stops when the end of the shortest @var{lst} is reached.
+The return index starts from 0 for the first set of elements. If no
+set of elements pass then the return is @code{#f}.
+
+@example
+(list-index odd? '(2 4 6 9)) @result{} 3
+(list-index = '(1 2 3) '(3 1 2)) @result{} #f
+@end example
@end deffn
@deffn {Scheme Procedure} member x lst [=]
Return the first sublist of @var{lst} whose @sc{car} is equal to
-@var{x}. If @var{x} does no appear in @var{lst}, return @code{#f}.
-Equality is determined by the equality predicate @var{=}, or
-@code{equal?} if @var{=} is not given.
+@var{x}. If @var{x} does not appear in @var{lst}, return @code{#f}.
-This function extends the core @code{member} by accepting an equality
-predicate. (@pxref{List Searching})
+Equality is determined by @code{equal?}, or by the equality predicate
+@var{=} if given. @var{=} is called @code{(= @var{x} elem)},
+ie.@: with the given @var{x} first, so for example to find the first
+element greater than 5,
+
+@example
+(member 5 '(3 5 1 7 2 9) <) @result{} (7 2 9)
+@end example
+
+This version of @code{member} extends the core @code{member}
+(@pxref{List Searching}) by accepting an equality predicate.
@end deffn
@subsubsection Deleting
@cindex list delete
-@c FIXME::martin: Review me!
-
@deffn {Scheme Procedure} delete x lst [=]
@deffnx {Scheme Procedure} delete! x lst [=]
Return a list containing the elements of @var{lst} but with those
common tail with @var{lst}. @code{delete!} may modify the structure
of @var{lst} to construct its return.
-These functions extend the core @code{delete} and @code{delete!} in
-accepting an equality predicate. (@pxref{List Modification})
+These functions extend the core @code{delete} and @code{delete!}
+(@pxref{List Modification}) in accepting an equality predicate. See
+also @code{lset-difference} (@pxref{SRFI-1 Set Operations}) for
+deleting multiple elements from a list.
@end deffn
@deffn {Scheme Procedure} delete-duplicates lst [=]
for dealing with association lists defined by SRFI-1.
@deffn {Scheme Procedure} assoc key alist [=]
-Return the pair from @var{alist} which matches @var{key}. Equality is
-determined by @var{=}, which defaults to @code{equal?} if not given.
-@var{alist} must be an association lists---a list of pairs.
+Return the pair from @var{alist} which matches @var{key}. This
+extends the core @code{assoc} (@pxref{Retrieving Alist Entries}) by
+taking an optional @var{=} comparison procedure.
+
+The default comparison is @code{equal?}. If an @var{=} parameter is
+given it's called @code{(@var{=} @var{key} @var{alistcar})}, i.e.@: the
+given target @var{key} is the first argument, and a @code{car} from
+@var{alist} is second.
+
+For example a case-insensitive string lookup,
-This function extends the core @code{assoc} by accepting an equality
-predicate. (@pxref{Association Lists})
+@example
+(assoc "yy" '(("XX" . 1) ("YY" . 2)) string-ci=?)
+@result{} ("YY" . 2)
+@end example
@end deffn
@deffn {Scheme Procedure} alist-cons key datum alist
-Equivalent to
+Cons a new association @var{key} and @var{datum} onto @var{alist} and
+return the result. This is equivalent to
@lisp
(cons (cons @var{key} @var{datum}) @var{alist})
@end lisp
-This procedure is used to coons a new pair onto an existing
-association list.
+@code{acons} (@pxref{Adding or Setting Alist Entries}) in the Guile
+core does the same thing.
@end deffn
@deffn {Scheme Procedure} alist-copy alist
Equality is determined by the @var{=} predicate, or @code{equal?} if
not given. The order in which elements are tested is unspecified, but
-each equality call is made @code{(= key alistkey)}, ie. the given
+each equality call is made @code{(= key alistkey)}, i.e.@: the given
@var{key} parameter is first and the key from @var{alist} second.
This means for instance all associations with a key greater than 5 can
be removed with @code{(alist-delete 5 alist <)}.
@subsubsection Set Operations on Lists
@cindex list set operation
-@c FIXME::martin: Review me!
+Lists can be used to represent sets of objects. The procedures in
+this section operate on such lists as sets.
-Lists can be used for representing sets of objects. The procedures
-documented in this section can be used for such set representations.
-Man combining several sets or adding elements, they make sure that no
-object is contained more than once in a given list. Please note that
-lists are not a too efficient implementation method for sets, so if
-you need high performance, you should think about implementing a
-custom data structure for representing sets, such as trees, bitsets,
-hash tables or something similar.
+Note that lists are not an efficient way to implement large sets. The
+procedures here typically take time @math{@var{m}@cross{}@var{n}} when
+operating on @var{m} and @var{n} element lists. Other data structures
+like trees, bitsets (@pxref{Bit Vectors}) or hash tables (@pxref{Hash
+Tables}) are faster.
-All these procedures accept an equality predicate as the first
-argument. This predicate is used for testing the objects in the list
-sets for sameness.
+All these procedures take an equality predicate as the first argument.
+This predicate is used for testing the objects in the list sets for
+sameness. This predicate must be consistent with @code{eq?}
+(@pxref{Equality}) in the sense that if two list elements are
+@code{eq?} then they must also be equal under the predicate. This
+simply means a given object must be equal to itself.
-@deffn {Scheme Procedure} lset<= = list1 @dots{}
-Return @code{#t} if every @var{listi} is a subset of @var{listi+1},
-otherwise return @code{#f}. Returns @code{#t} if called with less
-than two arguments. @var{=} is used for testing element equality.
+@deffn {Scheme Procedure} lset<= = list1 list2 @dots{}
+Return @code{#t} if each list is a subset of the one following it.
+Ie.@: @var{list1} a subset of @var{list2}, @var{list2} a subset of
+@var{list3}, etc, for as many lists as given. If only one list or no
+lists are given then the return is @code{#t}.
+
+A list @var{x} is a subset of @var{y} if each element of @var{x} is
+equal to some element in @var{y}. Elements are compared using the
+given @var{=} procedure, called as @code{(@var{=} xelem yelem)}.
+
+@example
+(lset<= eq?) @result{} #t
+(lset<= eqv? '(1 2 3) '(1)) @result{} #f
+(lset<= eqv? '(1 3 2) '(4 3 1 2)) @result{} #t
+@end example
@end deffn
@deffn {Scheme Procedure} lset= = list1 list2 @dots{}
-Return @code{#t} if all argument lists are equal. @var{=} is used for
-testing element equality.
+Return @code{#t} if all argument lists are set-equal. @var{list1} is
+compared to @var{list2}, @var{list2} to @var{list3}, etc, for as many
+lists as given. If only one list or no lists are given then the
+return is @code{#t}.
+
+Two lists @var{x} and @var{y} are set-equal if each element of @var{x}
+is equal to some element of @var{y} and conversely each element of
+@var{y} is equal to some element of @var{x}. The order of the
+elements in the lists doesn't matter. Element equality is determined
+with the given @var{=} procedure, called as @code{(@var{=} xelem
+yelem)}, but exactly which calls are made is unspecified.
+
+@example
+(lset= eq?) @result{} #t
+(lset= eqv? '(1 2 3) '(3 2 1)) @result{} #t
+(lset= string-ci=? '("a" "A" "b") '("B" "b" "a")) @result{} #t
+@end example
@end deffn
-@deffn {Scheme Procedure} lset-adjoin = list elt1 @dots{}
-@deffnx {Scheme Procedure} lset-adjoin! = list elt1 @dots{}
-Add all @var{elts} to the list @var{list}, suppressing duplicates and
-return the resulting list. @code{lset-adjoin!} is allowed, but not
-required to modify its first argument. @var{=} is used for testing
-element equality.
+@deffn {Scheme Procedure} lset-adjoin = list elem1 @dots{}
+Add to @var{list} any of the given @var{elem}s not already in the
+list. @var{elem}s are @code{cons}ed onto the start of @var{list} (so
+the return shares a common tail with @var{list}), but the order
+they're added is unspecified.
+
+The given @var{=} procedure is used for comparing elements, called as
+@code{(@var{=} listelem elem)}, ie.@: the second argument is one of
+the given @var{elem} parameters.
+
+@example
+(lset-adjoin eqv? '(1 2 3) 4 1 5) @result{} (5 4 1 2 3)
+@end example
@end deffn
-@deffn {Scheme Procedure} lset-union = list1 @dots{}
-@deffnx {Scheme Procedure} lset-union! = list1 @dots{}
-Return the union of all argument list sets. The union is the set of
-all elements which appear in any of the argument sets.
-@code{lset-union!} is allowed, but not required to modify its first
-argument. @var{=} is used for testing element equality.
+@deffn {Scheme Procedure} lset-union = list1 list2 @dots{}
+@deffnx {Scheme Procedure} lset-union! = list1 list2 @dots{}
+Return the union of the argument list sets. The result is built by
+taking the union of @var{list1} and @var{list2}, then the union of
+that with @var{list3}, etc, for as many lists as given. For one list
+argument that list itself is the result, for no list arguments the
+result is the empty list.
+
+The union of two lists @var{x} and @var{y} is formed as follows. If
+@var{x} is empty then the result is @var{y}. Otherwise start with
+@var{x} as the result and consider each @var{y} element (from first to
+last). A @var{y} element not equal to something already in the result
+is @code{cons}ed onto the result.
+
+The given @var{=} procedure is used for comparing elements, called as
+@code{(@var{=} relem yelem)}. The first argument is from the result
+accumulated so far, and the second is from the list being union-ed in.
+But exactly which calls are made is otherwise unspecified.
+
+Notice that duplicate elements in @var{list1} (or the first non-empty
+list) are preserved, but that repeated elements in subsequent lists
+are only added once.
+
+@example
+(lset-union eqv?) @result{} ()
+(lset-union eqv? '(1 2 3)) @result{} (1 2 3)
+(lset-union eqv? '(1 2 1 3) '(2 4 5) '(5)) @result{} (5 4 1 2 1 3)
+@end example
+
+@code{lset-union} doesn't change the given lists but the result may
+share a tail with the first non-empty list. @code{lset-union!} can
+modify all of the given lists to form the result.
@end deffn
@deffn {Scheme Procedure} lset-intersection = list1 list2 @dots{}
@deffnx {Scheme Procedure} lset-intersection! = list1 list2 @dots{}
-Return the intersection of all argument list sets. The intersection
-is the set containing all elements which appear in all argument sets.
-@code{lset-intersection!} is allowed, but not required to modify its
-first argument. @var{=} is used for testing element equality.
+Return the intersection of @var{list1} with the other argument lists,
+meaning those elements of @var{list1} which are also in all of
+@var{list2} etc. For one list argument, just that list is returned.
+
+The test for an element of @var{list1} to be in the return is simply
+that it's equal to some element in each of @var{list2} etc. Notice
+this means an element appearing twice in @var{list1} but only once in
+each of @var{list2} etc will go into the return twice. The return has
+its elements in the same order as they were in @var{list1}.
+
+The given @var{=} procedure is used for comparing elements, called as
+@code{(@var{=} elem1 elemN)}. The first argument is from @var{list1}
+and the second is from one of the subsequent lists. But exactly which
+calls are made and in what order is unspecified.
+
+@example
+(lset-intersection eqv? '(x y)) @result{} (x y)
+(lset-intersection eqv? '(1 2 3) '(4 3 2)) @result{} (2 3)
+(lset-intersection eqv? '(1 1 2 2) '(1 2) '(2 1) '(2)) @result{} (2 2)
+@end example
+
+The return from @code{lset-intersection} may share a tail with
+@var{list1}. @code{lset-intersection!} may modify @var{list1} to form
+its result.
@end deffn
@deffn {Scheme Procedure} lset-difference = list1 list2 @dots{}
@deffnx {Scheme Procedure} lset-difference! = list1 list2 @dots{}
-Return the difference of all argument list sets. The difference is
-the the set containing all elements of the first list which do not
-appear in the other lists. @code{lset-difference!} is allowed, but
-not required to modify its first argument. @var{=} is used for testing
-element equality.
-@end deffn
+Return @var{list1} with any elements in @var{list2}, @var{list3} etc
+removed (ie.@: subtracted). For one list argument, just that list is
+returned.
+
+The given @var{=} procedure is used for comparing elements, called as
+@code{(@var{=} elem1 elemN)}. The first argument is from @var{list1}
+and the second from one of the subsequent lists. But exactly which
+calls are made and in what order is unspecified.
+
+@example
+(lset-difference eqv? '(x y)) @result{} (x y)
+(lset-difference eqv? '(1 2 3) '(3 1)) @result{} (2)
+(lset-difference eqv? '(1 2 3) '(3) '(2)) @result{} (1)
+@end example
-@deffn {Scheme Procedure} lset-xor = list1 @dots{}
-@deffnx {Scheme Procedure} lset-xor! = list1 @dots{}
-Return the set containing all elements which appear in the first
-argument list set, but not in the second; or, more generally: which
-appear in an odd number of sets. @code{lset-xor!} is allowed, but
-not required to modify its first argument. @var{=} is used for testing
-element equality.
+The return from @code{lset-difference} may share a tail with
+@var{list1}. @code{lset-difference!} may modify @var{list1} to form
+its result.
@end deffn
@deffn {Scheme Procedure} lset-diff+intersection = list1 list2 @dots{}
@deffnx {Scheme Procedure} lset-diff+intersection! = list1 list2 @dots{}
-Return two values, the difference and the intersection of the argument
-list sets. This works like a combination of @code{lset-difference} and
-@code{lset-intersection}, but is more efficient.
-@code{lset-diff+intersection!} is allowed, but not required to modify
-its first argument. @var{=} is used for testing element equality. You
-have to use some means to deal with the multiple values these
-procedures return (@pxref{Multiple Values}).
+Return two values (@pxref{Multiple Values}), the difference and
+intersection of the argument lists as per @code{lset-difference} and
+@code{lset-intersection} above.
+
+For two list arguments this partitions @var{list1} into those elements
+of @var{list1} which are in @var{list2} and not in @var{list2}. (But
+for more than two arguments there can be elements of @var{list1} which
+are neither part of the difference nor the intersection.)
+
+One of the return values from @code{lset-diff+intersection} may share
+a tail with @var{list1}. @code{lset-diff+intersection!} may modify
+@var{list1} to form its results.
+@end deffn
+
+@deffn {Scheme Procedure} lset-xor = list1 list2 @dots{}
+@deffnx {Scheme Procedure} lset-xor! = list1 list2 @dots{}
+Return an XOR of the argument lists. For two lists this means those
+elements which are in exactly one of the lists. For more than two
+lists it means those elements which appear in an odd number of the
+lists.
+
+To be precise, the XOR of two lists @var{x} and @var{y} is formed by
+taking those elements of @var{x} not equal to any element of @var{y},
+plus those elements of @var{y} not equal to any element of @var{x}.
+Equality is determined with the given @var{=} procedure, called as
+@code{(@var{=} e1 e2)}. One argument is from @var{x} and the other
+from @var{y}, but which way around is unspecified. Exactly which
+calls are made is also unspecified, as is the order of the elements in
+the result.
+
+@example
+(lset-xor eqv? '(x y)) @result{} (x y)
+(lset-xor eqv? '(1 2 3) '(4 3 2)) @result{} (4 1)
+@end example
+
+The return from @code{lset-xor} may share a tail with one of the list
+arguments. @code{lset-xor!} may modify @var{list1} to form its
+result.
@end deffn
@subsection SRFI-4 - Homogeneous numeric vector datatypes
@cindex SRFI-4
-The SRFI-4 procedures and data types are always available, @xref{Uniform
-Numeric Vectors}.
+SRFI-4 provides an interface to uniform numeric vectors: vectors whose elements
+are all of a single numeric type. Guile offers uniform numeric vectors for
+signed and unsigned 8-bit, 16-bit, 32-bit, and 64-bit integers, two sizes of
+floating point values, and, as an extension to SRFI-4, complex floating-point
+numbers of these two sizes.
+
+The standard SRFI-4 procedures and data types may be included via loading the
+appropriate module:
+
+@example
+(use-modules (srfi srfi-4))
+@end example
+
+This module is currently a part of the default Guile environment, but it is a
+good practice to explicitly import the module. In the future, using SRFI-4
+procedures without importing the SRFI-4 module will cause a deprecation message
+to be printed. (Of course, one may call the C functions at any time. Would that
+C had modules!)
+
+@menu
+* SRFI-4 Overview:: The warp and weft of uniform numeric vectors.
+* SRFI-4 API:: Uniform vectors, from Scheme and from C.
+* SRFI-4 Generic Operations:: The general, operating on the specific.
+* SRFI-4 and Bytevectors:: SRFI-4 vectors are backed by bytevectors.
+* SRFI-4 Extensions:: Guile-specific extensions to the standard.
+@end menu
+
+@node SRFI-4 Overview
+@subsubsection SRFI-4 - Overview
+
+Uniform numeric vectors can be useful since they consume less memory
+than the non-uniform, general vectors. Also, since the types they can
+store correspond directly to C types, it is easier to work with them
+efficiently on a low level. Consider image processing as an example,
+where you want to apply a filter to some image. While you could store
+the pixels of an image in a general vector and write a general
+convolution function, things are much more efficient with uniform
+vectors: the convolution function knows that all pixels are unsigned
+8-bit values (say), and can use a very tight inner loop.
+
+This is implemented in Scheme by having the compiler notice calls to the SRFI-4
+accessors, and inline them to appropriate compiled code. From C you have access
+to the raw array; functions for efficiently working with uniform numeric vectors
+from C are listed at the end of this section.
+
+Uniform numeric vectors are the special case of one dimensional uniform
+numeric arrays.
+
+There are 12 standard kinds of uniform numeric vectors, and they all have their
+own complement of constructors, accessors, and so on. Procedures that operate on
+a specific kind of uniform numeric vector have a ``tag'' in their name,
+indicating the element type.
+
+@table @nicode
+@item u8
+unsigned 8-bit integers
+
+@item s8
+signed 8-bit integers
+
+@item u16
+unsigned 16-bit integers
+
+@item s16
+signed 16-bit integers
+
+@item u32
+unsigned 32-bit integers
+
+@item s32
+signed 32-bit integers
+
+@item u64
+unsigned 64-bit integers
+
+@item s64
+signed 64-bit integers
+
+@item f32
+the C type @code{float}
+
+@item f64
+the C type @code{double}
+
+@end table
+
+In addition, Guile supports uniform arrays of complex numbers, with the
+nonstandard tags:
+
+@table @nicode
+
+@item c32
+complex numbers in rectangular form with the real and imaginary part
+being a @code{float}
+
+@item c64
+complex numbers in rectangular form with the real and imaginary part
+being a @code{double}
+
+@end table
+
+The external representation (ie.@: read syntax) for these vectors is
+similar to normal Scheme vectors, but with an additional tag from the
+tables above indicating the vector's type. For example,
+
+@lisp
+#u16(1 2 3)
+#f64(3.1415 2.71)
+@end lisp
+
+Note that the read syntax for floating-point here conflicts with
+@code{#f} for false. In Standard Scheme one can write @code{(1 #f3)}
+for a three element list @code{(1 #f 3)}, but for Guile @code{(1 #f3)}
+is invalid. @code{(1 #f 3)} is almost certainly what one should write
+anyway to make the intention clear, so this is rarely a problem.
+
+
+@node SRFI-4 API
+@subsubsection SRFI-4 - API
+
+Note that the @nicode{c32} and @nicode{c64} functions are only available from
+@nicode{(srfi srfi-4 gnu)}.
+
+@deffn {Scheme Procedure} u8vector? obj
+@deffnx {Scheme Procedure} s8vector? obj
+@deffnx {Scheme Procedure} u16vector? obj
+@deffnx {Scheme Procedure} s16vector? obj
+@deffnx {Scheme Procedure} u32vector? obj
+@deffnx {Scheme Procedure} s32vector? obj
+@deffnx {Scheme Procedure} u64vector? obj
+@deffnx {Scheme Procedure} s64vector? obj
+@deffnx {Scheme Procedure} f32vector? obj
+@deffnx {Scheme Procedure} f64vector? obj
+@deffnx {Scheme Procedure} c32vector? obj
+@deffnx {Scheme Procedure} c64vector? obj
+@deffnx {C Function} scm_u8vector_p (obj)
+@deffnx {C Function} scm_s8vector_p (obj)
+@deffnx {C Function} scm_u16vector_p (obj)
+@deffnx {C Function} scm_s16vector_p (obj)
+@deffnx {C Function} scm_u32vector_p (obj)
+@deffnx {C Function} scm_s32vector_p (obj)
+@deffnx {C Function} scm_u64vector_p (obj)
+@deffnx {C Function} scm_s64vector_p (obj)
+@deffnx {C Function} scm_f32vector_p (obj)
+@deffnx {C Function} scm_f64vector_p (obj)
+@deffnx {C Function} scm_c32vector_p (obj)
+@deffnx {C Function} scm_c64vector_p (obj)
+Return @code{#t} if @var{obj} is a homogeneous numeric vector of the
+indicated type.
+@end deffn
+
+@deffn {Scheme Procedure} make-u8vector n [value]
+@deffnx {Scheme Procedure} make-s8vector n [value]
+@deffnx {Scheme Procedure} make-u16vector n [value]
+@deffnx {Scheme Procedure} make-s16vector n [value]
+@deffnx {Scheme Procedure} make-u32vector n [value]
+@deffnx {Scheme Procedure} make-s32vector n [value]
+@deffnx {Scheme Procedure} make-u64vector n [value]
+@deffnx {Scheme Procedure} make-s64vector n [value]
+@deffnx {Scheme Procedure} make-f32vector n [value]
+@deffnx {Scheme Procedure} make-f64vector n [value]
+@deffnx {Scheme Procedure} make-c32vector n [value]
+@deffnx {Scheme Procedure} make-c64vector n [value]
+@deffnx {C Function} scm_make_u8vector n [value]
+@deffnx {C Function} scm_make_s8vector n [value]
+@deffnx {C Function} scm_make_u16vector n [value]
+@deffnx {C Function} scm_make_s16vector n [value]
+@deffnx {C Function} scm_make_u32vector n [value]
+@deffnx {C Function} scm_make_s32vector n [value]
+@deffnx {C Function} scm_make_u64vector n [value]
+@deffnx {C Function} scm_make_s64vector n [value]
+@deffnx {C Function} scm_make_f32vector n [value]
+@deffnx {C Function} scm_make_f64vector n [value]
+@deffnx {C Function} scm_make_c32vector n [value]
+@deffnx {C Function} scm_make_c64vector n [value]
+Return a newly allocated homogeneous numeric vector holding @var{n}
+elements of the indicated type. If @var{value} is given, the vector
+is initialized with that value, otherwise the contents are
+unspecified.
+@end deffn
+
+@deffn {Scheme Procedure} u8vector value @dots{}
+@deffnx {Scheme Procedure} s8vector value @dots{}
+@deffnx {Scheme Procedure} u16vector value @dots{}
+@deffnx {Scheme Procedure} s16vector value @dots{}
+@deffnx {Scheme Procedure} u32vector value @dots{}
+@deffnx {Scheme Procedure} s32vector value @dots{}
+@deffnx {Scheme Procedure} u64vector value @dots{}
+@deffnx {Scheme Procedure} s64vector value @dots{}
+@deffnx {Scheme Procedure} f32vector value @dots{}
+@deffnx {Scheme Procedure} f64vector value @dots{}
+@deffnx {Scheme Procedure} c32vector value @dots{}
+@deffnx {Scheme Procedure} c64vector value @dots{}
+@deffnx {C Function} scm_u8vector (values)
+@deffnx {C Function} scm_s8vector (values)
+@deffnx {C Function} scm_u16vector (values)
+@deffnx {C Function} scm_s16vector (values)
+@deffnx {C Function} scm_u32vector (values)
+@deffnx {C Function} scm_s32vector (values)
+@deffnx {C Function} scm_u64vector (values)
+@deffnx {C Function} scm_s64vector (values)
+@deffnx {C Function} scm_f32vector (values)
+@deffnx {C Function} scm_f64vector (values)
+@deffnx {C Function} scm_c32vector (values)
+@deffnx {C Function} scm_c64vector (values)
+Return a newly allocated homogeneous numeric vector of the indicated
+type, holding the given parameter @var{value}s. The vector length is
+the number of parameters given.
+@end deffn
+
+@deffn {Scheme Procedure} u8vector-length vec
+@deffnx {Scheme Procedure} s8vector-length vec
+@deffnx {Scheme Procedure} u16vector-length vec
+@deffnx {Scheme Procedure} s16vector-length vec
+@deffnx {Scheme Procedure} u32vector-length vec
+@deffnx {Scheme Procedure} s32vector-length vec
+@deffnx {Scheme Procedure} u64vector-length vec
+@deffnx {Scheme Procedure} s64vector-length vec
+@deffnx {Scheme Procedure} f32vector-length vec
+@deffnx {Scheme Procedure} f64vector-length vec
+@deffnx {Scheme Procedure} c32vector-length vec
+@deffnx {Scheme Procedure} c64vector-length vec
+@deffnx {C Function} scm_u8vector_length (vec)
+@deffnx {C Function} scm_s8vector_length (vec)
+@deffnx {C Function} scm_u16vector_length (vec)
+@deffnx {C Function} scm_s16vector_length (vec)
+@deffnx {C Function} scm_u32vector_length (vec)
+@deffnx {C Function} scm_s32vector_length (vec)
+@deffnx {C Function} scm_u64vector_length (vec)
+@deffnx {C Function} scm_s64vector_length (vec)
+@deffnx {C Function} scm_f32vector_length (vec)
+@deffnx {C Function} scm_f64vector_length (vec)
+@deffnx {C Function} scm_c32vector_length (vec)
+@deffnx {C Function} scm_c64vector_length (vec)
+Return the number of elements in @var{vec}.
+@end deffn
+
+@deffn {Scheme Procedure} u8vector-ref vec i
+@deffnx {Scheme Procedure} s8vector-ref vec i
+@deffnx {Scheme Procedure} u16vector-ref vec i
+@deffnx {Scheme Procedure} s16vector-ref vec i
+@deffnx {Scheme Procedure} u32vector-ref vec i
+@deffnx {Scheme Procedure} s32vector-ref vec i
+@deffnx {Scheme Procedure} u64vector-ref vec i
+@deffnx {Scheme Procedure} s64vector-ref vec i
+@deffnx {Scheme Procedure} f32vector-ref vec i
+@deffnx {Scheme Procedure} f64vector-ref vec i
+@deffnx {Scheme Procedure} c32vector-ref vec i
+@deffnx {Scheme Procedure} c64vector-ref vec i
+@deffnx {C Function} scm_u8vector_ref (vec i)
+@deffnx {C Function} scm_s8vector_ref (vec i)
+@deffnx {C Function} scm_u16vector_ref (vec i)
+@deffnx {C Function} scm_s16vector_ref (vec i)
+@deffnx {C Function} scm_u32vector_ref (vec i)
+@deffnx {C Function} scm_s32vector_ref (vec i)
+@deffnx {C Function} scm_u64vector_ref (vec i)
+@deffnx {C Function} scm_s64vector_ref (vec i)
+@deffnx {C Function} scm_f32vector_ref (vec i)
+@deffnx {C Function} scm_f64vector_ref (vec i)
+@deffnx {C Function} scm_c32vector_ref (vec i)
+@deffnx {C Function} scm_c64vector_ref (vec i)
+Return the element at index @var{i} in @var{vec}. The first element
+in @var{vec} is index 0.
+@end deffn
+
+@deffn {Scheme Procedure} u8vector-set! vec i value
+@deffnx {Scheme Procedure} s8vector-set! vec i value
+@deffnx {Scheme Procedure} u16vector-set! vec i value
+@deffnx {Scheme Procedure} s16vector-set! vec i value
+@deffnx {Scheme Procedure} u32vector-set! vec i value
+@deffnx {Scheme Procedure} s32vector-set! vec i value
+@deffnx {Scheme Procedure} u64vector-set! vec i value
+@deffnx {Scheme Procedure} s64vector-set! vec i value
+@deffnx {Scheme Procedure} f32vector-set! vec i value
+@deffnx {Scheme Procedure} f64vector-set! vec i value
+@deffnx {Scheme Procedure} c32vector-set! vec i value
+@deffnx {Scheme Procedure} c64vector-set! vec i value
+@deffnx {C Function} scm_u8vector_set_x (vec i value)
+@deffnx {C Function} scm_s8vector_set_x (vec i value)
+@deffnx {C Function} scm_u16vector_set_x (vec i value)
+@deffnx {C Function} scm_s16vector_set_x (vec i value)
+@deffnx {C Function} scm_u32vector_set_x (vec i value)
+@deffnx {C Function} scm_s32vector_set_x (vec i value)
+@deffnx {C Function} scm_u64vector_set_x (vec i value)
+@deffnx {C Function} scm_s64vector_set_x (vec i value)
+@deffnx {C Function} scm_f32vector_set_x (vec i value)
+@deffnx {C Function} scm_f64vector_set_x (vec i value)
+@deffnx {C Function} scm_c32vector_set_x (vec i value)
+@deffnx {C Function} scm_c64vector_set_x (vec i value)
+Set the element at index @var{i} in @var{vec} to @var{value}. The
+first element in @var{vec} is index 0. The return value is
+unspecified.
+@end deffn
+
+@deffn {Scheme Procedure} u8vector->list vec
+@deffnx {Scheme Procedure} s8vector->list vec
+@deffnx {Scheme Procedure} u16vector->list vec
+@deffnx {Scheme Procedure} s16vector->list vec
+@deffnx {Scheme Procedure} u32vector->list vec
+@deffnx {Scheme Procedure} s32vector->list vec
+@deffnx {Scheme Procedure} u64vector->list vec
+@deffnx {Scheme Procedure} s64vector->list vec
+@deffnx {Scheme Procedure} f32vector->list vec
+@deffnx {Scheme Procedure} f64vector->list vec
+@deffnx {Scheme Procedure} c32vector->list vec
+@deffnx {Scheme Procedure} c64vector->list vec
+@deffnx {C Function} scm_u8vector_to_list (vec)
+@deffnx {C Function} scm_s8vector_to_list (vec)
+@deffnx {C Function} scm_u16vector_to_list (vec)
+@deffnx {C Function} scm_s16vector_to_list (vec)
+@deffnx {C Function} scm_u32vector_to_list (vec)
+@deffnx {C Function} scm_s32vector_to_list (vec)
+@deffnx {C Function} scm_u64vector_to_list (vec)
+@deffnx {C Function} scm_s64vector_to_list (vec)
+@deffnx {C Function} scm_f32vector_to_list (vec)
+@deffnx {C Function} scm_f64vector_to_list (vec)
+@deffnx {C Function} scm_c32vector_to_list (vec)
+@deffnx {C Function} scm_c64vector_to_list (vec)
+Return a newly allocated list holding all elements of @var{vec}.
+@end deffn
+
+@deffn {Scheme Procedure} list->u8vector lst
+@deffnx {Scheme Procedure} list->s8vector lst
+@deffnx {Scheme Procedure} list->u16vector lst
+@deffnx {Scheme Procedure} list->s16vector lst
+@deffnx {Scheme Procedure} list->u32vector lst
+@deffnx {Scheme Procedure} list->s32vector lst
+@deffnx {Scheme Procedure} list->u64vector lst
+@deffnx {Scheme Procedure} list->s64vector lst
+@deffnx {Scheme Procedure} list->f32vector lst
+@deffnx {Scheme Procedure} list->f64vector lst
+@deffnx {Scheme Procedure} list->c32vector lst
+@deffnx {Scheme Procedure} list->c64vector lst
+@deffnx {C Function} scm_list_to_u8vector (lst)
+@deffnx {C Function} scm_list_to_s8vector (lst)
+@deffnx {C Function} scm_list_to_u16vector (lst)
+@deffnx {C Function} scm_list_to_s16vector (lst)
+@deffnx {C Function} scm_list_to_u32vector (lst)
+@deffnx {C Function} scm_list_to_s32vector (lst)
+@deffnx {C Function} scm_list_to_u64vector (lst)
+@deffnx {C Function} scm_list_to_s64vector (lst)
+@deffnx {C Function} scm_list_to_f32vector (lst)
+@deffnx {C Function} scm_list_to_f64vector (lst)
+@deffnx {C Function} scm_list_to_c32vector (lst)
+@deffnx {C Function} scm_list_to_c64vector (lst)
+Return a newly allocated homogeneous numeric vector of the indicated type,
+initialized with the elements of the list @var{lst}.
+@end deffn
+
+@deftypefn {C Function} SCM scm_take_u8vector (const scm_t_uint8 *data, size_t len)
+@deftypefnx {C Function} SCM scm_take_s8vector (const scm_t_int8 *data, size_t len)
+@deftypefnx {C Function} SCM scm_take_u16vector (const scm_t_uint16 *data, size_t len)
+@deftypefnx {C Function} SCM scm_take_s16vector (const scm_t_int16 *data, size_t len)
+@deftypefnx {C Function} SCM scm_take_u32vector (const scm_t_uint32 *data, size_t len)
+@deftypefnx {C Function} SCM scm_take_s32vector (const scm_t_int32 *data, size_t len)
+@deftypefnx {C Function} SCM scm_take_u64vector (const scm_t_uint64 *data, size_t len)
+@deftypefnx {C Function} SCM scm_take_s64vector (const scm_t_int64 *data, size_t len)
+@deftypefnx {C Function} SCM scm_take_f32vector (const float *data, size_t len)
+@deftypefnx {C Function} SCM scm_take_f64vector (const double *data, size_t len)
+@deftypefnx {C Function} SCM scm_take_c32vector (const float *data, size_t len)
+@deftypefnx {C Function} SCM scm_take_c64vector (const double *data, size_t len)
+Return a new uniform numeric vector of the indicated type and length
+that uses the memory pointed to by @var{data} to store its elements.
+This memory will eventually be freed with @code{free}. The argument
+@var{len} specifies the number of elements in @var{data}, not its size
+in bytes.
+
+The @code{c32} and @code{c64} variants take a pointer to a C array of
+@code{float}s or @code{double}s. The real parts of the complex numbers
+are at even indices in that array, the corresponding imaginary parts are
+at the following odd index.
+@end deftypefn
+
+@deftypefn {C Function} {const scm_t_uint8 *} scm_u8vector_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
+@deftypefnx {C Function} {const scm_t_int8 *} scm_s8vector_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
+@deftypefnx {C Function} {const scm_t_uint16 *} scm_u16vector_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
+@deftypefnx {C Function} {const scm_t_int16 *} scm_s16vector_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
+@deftypefnx {C Function} {const scm_t_uint32 *} scm_u32vector_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
+@deftypefnx {C Function} {const scm_t_int32 *} scm_s32vector_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
+@deftypefnx {C Function} {const scm_t_uint64 *} scm_u64vector_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
+@deftypefnx {C Function} {const scm_t_int64 *} scm_s64vector_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
+@deftypefnx {C Function} {const float *} scm_f32vector_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
+@deftypefnx {C Function} {const double *} scm_f64vector_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
+@deftypefnx {C Function} {const float *} scm_c32vector_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
+@deftypefnx {C Function} {const double *} scm_c64vector_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
+Like @code{scm_vector_elements} (@pxref{Vector Accessing from C}), but
+returns a pointer to the elements of a uniform numeric vector of the
+indicated kind.
+@end deftypefn
+
+@deftypefn {C Function} {scm_t_uint8 *} scm_u8vector_writable_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
+@deftypefnx {C Function} {scm_t_int8 *} scm_s8vector_writable_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
+@deftypefnx {C Function} {scm_t_uint16 *} scm_u16vector_writable_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
+@deftypefnx {C Function} {scm_t_int16 *} scm_s16vector_writable_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
+@deftypefnx {C Function} {scm_t_uint32 *} scm_u32vector_writable_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
+@deftypefnx {C Function} {scm_t_int32 *} scm_s32vector_writable_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
+@deftypefnx {C Function} {scm_t_uint64 *} scm_u64vector_writable_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
+@deftypefnx {C Function} {scm_t_int64 *} scm_s64vector_writable_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
+@deftypefnx {C Function} {float *} scm_f32vector_writable_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
+@deftypefnx {C Function} {double *} scm_f64vector_writable_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
+@deftypefnx {C Function} {float *} scm_c32vector_writable_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
+@deftypefnx {C Function} {double *} scm_c64vector_writable_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
+Like @code{scm_vector_writable_elements} (@pxref{Vector Accessing from
+C}), but returns a pointer to the elements of a uniform numeric vector
+of the indicated kind.
+@end deftypefn
+
+@node SRFI-4 Generic Operations
+@subsubsection SRFI-4 - Generic operations
+
+Guile also provides procedures that operate on all types of uniform numeric
+vectors. In what is probably a bug, these procedures are currently available in
+the default environment as well; however prudent hackers will make sure to
+import @code{(srfi srfi-4 gnu)} before using these.
+
+@deftypefn {C Function} int scm_is_uniform_vector (SCM uvec)
+Return non-zero when @var{uvec} is a uniform numeric vector, zero
+otherwise.
+@end deftypefn
+
+@deftypefn {C Function} size_t scm_c_uniform_vector_length (SCM uvec)
+Return the number of elements of @var{uvec} as a @code{size_t}.
+@end deftypefn
+
+@deffn {Scheme Procedure} uniform-vector? obj
+@deffnx {C Function} scm_uniform_vector_p (obj)
+Return @code{#t} if @var{obj} is a homogeneous numeric vector of the
+indicated type.
+@end deffn
+
+@deffn {Scheme Procedure} uniform-vector-length vec
+@deffnx {C Function} scm_uniform_vector_length (vec)
+Return the number of elements in @var{vec}.
+@end deffn
+
+@deffn {Scheme Procedure} uniform-vector-ref vec i
+@deffnx {C Function} scm_uniform_vector_ref (vec i)
+Return the element at index @var{i} in @var{vec}. The first element
+in @var{vec} is index 0.
+@end deffn
+
+@deffn {Scheme Procedure} uniform-vector-set! vec i value
+@deffnx {C Function} scm_uniform_vector_set_x (vec i value)
+Set the element at index @var{i} in @var{vec} to @var{value}. The
+first element in @var{vec} is index 0. The return value is
+unspecified.
+@end deffn
+
+@deffn {Scheme Procedure} uniform-vector->list vec
+@deffnx {C Function} scm_uniform_vector_to_list (vec)
+Return a newly allocated list holding all elements of @var{vec}.
+@end deffn
+
+@deftypefn {C Function} {const void *} scm_uniform_vector_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
+Like @code{scm_vector_elements} (@pxref{Vector Accessing from C}), but
+returns a pointer to the elements of a uniform numeric vector.
+@end deftypefn
+
+@deftypefn {C Function} {void *} scm_uniform_vector_writable_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
+Like @code{scm_vector_writable_elements} (@pxref{Vector Accessing from
+C}), but returns a pointer to the elements of a uniform numeric vector.
+@end deftypefn
+
+Unless you really need to the limited generality of these functions, it is best
+to use the type-specific functions, or the generalized vector accessors.
+
+@node SRFI-4 and Bytevectors
+@subsubsection SRFI-4 - Relation to bytevectors
+
+Guile implements SRFI-4 vectors using bytevectors (@pxref{Bytevectors}). Often
+when you have a numeric vector, you end up wanting to write its bytes somewhere,
+or have access to the underlying bytes, or read in bytes from somewhere else.
+Bytevectors are very good at this sort of thing. But the SRFI-4 APIs are nicer
+to use when doing number-crunching, because they are addressed by element and
+not by byte.
+
+So as a compromise, Guile allows all bytevector functions to operate on numeric
+vectors. They address the underlying bytes in the native endianness, as one
+would expect.
+
+Following the same reasoning, that it's just bytes underneath, Guile also allows
+uniform vectors of a given type to be accessed as if they were of any type. One
+can fill a @nicode{u32vector}, and access its elements with
+@nicode{u8vector-ref}. One can use @nicode{f64vector-ref} on bytevectors. It's
+all the same to Guile.
+
+In this way, uniform numeric vectors may be written to and read from
+input/output ports using the procedures that operate on bytevectors.
+
+@xref{Bytevectors}, for more information.
+
+
+@node SRFI-4 Extensions
+@subsubsection SRFI-4 - Guile extensions
+
+Guile defines some useful extensions to SRFI-4, which are not available in the
+default Guile environment. They may be imported by loading the extensions
+module:
+
+@example
+(use-modules (srfi srfi-4 gnu))
+@end example
+
+@deffn {Scheme Procedure} any->u8vector obj
+@deffnx {Scheme Procedure} any->s8vector obj
+@deffnx {Scheme Procedure} any->u16vector obj
+@deffnx {Scheme Procedure} any->s16vector obj
+@deffnx {Scheme Procedure} any->u32vector obj
+@deffnx {Scheme Procedure} any->s32vector obj
+@deffnx {Scheme Procedure} any->u64vector obj
+@deffnx {Scheme Procedure} any->s64vector obj
+@deffnx {Scheme Procedure} any->f32vector obj
+@deffnx {Scheme Procedure} any->f64vector obj
+@deffnx {Scheme Procedure} any->c32vector obj
+@deffnx {Scheme Procedure} any->c64vector obj
+@deffnx {C Function} scm_any_to_u8vector (obj)
+@deffnx {C Function} scm_any_to_s8vector (obj)
+@deffnx {C Function} scm_any_to_u16vector (obj)
+@deffnx {C Function} scm_any_to_s16vector (obj)
+@deffnx {C Function} scm_any_to_u32vector (obj)
+@deffnx {C Function} scm_any_to_s32vector (obj)
+@deffnx {C Function} scm_any_to_u64vector (obj)
+@deffnx {C Function} scm_any_to_s64vector (obj)
+@deffnx {C Function} scm_any_to_f32vector (obj)
+@deffnx {C Function} scm_any_to_f64vector (obj)
+@deffnx {C Function} scm_any_to_c32vector (obj)
+@deffnx {C Function} scm_any_to_c64vector (obj)
+Return a (maybe newly allocated) uniform numeric vector of the indicated
+type, initialized with the elements of @var{obj}, which must be a list,
+a vector, or a uniform vector. When @var{obj} is already a suitable
+uniform numeric vector, it is returned unchanged.
+@end deffn
+
@node SRFI-6
@subsection SRFI-6 - Basic String Ports
the core @code{record-type-fields} etc, and are referred to in the
subsequent accessor/modifier forms.
-@var{predictate} is bound to a function to be called as
+@var{predicate} is bound to a function to be called as
@code{(@var{predicate} obj)}. It returns @code{#t} or @code{#f}
according to whether @var{obj} is a record of this type.
top-level @code{define}s. They can be redefined or @code{set!} as
desired, exported from a module, etc.
+@unnumberedsubsubsec Non-toplevel Record Definitions
+
+The SRFI-9 specification explicitly disallows record definitions in a
+non-toplevel context, such as inside @code{lambda} body or inside a
+@var{let} block. However, Guile's implementation does not enforce that
+restriction.
+
+@unnumberedsubsubsec Custom Printers
+
+You may use @code{set-record-type-printer!} to customize the default printing
+behavior of records. This is a Guile extension and is not part of SRFI-9. It
+is located in the @nicode{(srfi srfi-9 gnu)} module.
+
+@deffn {Scheme Syntax} set-record-type-printer! name thunk
+Where @var{type} corresponds to the first argument of @code{define-record-type},
+and @var{thunk} is a procedure accepting two arguments, the record to print, and
+an output port.
+@end deffn
+
+@noindent
+This example prints the employee's name in brackets, for instance @code{[Fred]}.
+
+@example
+(set-record-type-printer! employee-type
+ (lambda (record port)
+ (write-char #\[ port)
+ (display (get-employee-name record) port)
+ (write-char #\] port)))
+@end example
@node SRFI-10
@subsection SRFI-10 - Hash-Comma Reader Extension
@deffn {Scheme Procedure} define-reader-ctor tag proc
Register @var{proc} as the constructor for a hash-comma read syntax
-starting with symbol @var{tag}, ie. @nicode{#,(@var{tag} arg@dots{})}.
+starting with symbol @var{tag}, i.e.@: @nicode{#,(@var{tag} arg@dots{})}.
@var{proc} is called with the given arguments @code{(@var{proc}
arg@dots{})} and the object it returns is the result of the read.
@end deffn
(lambda elems
(let ((table (make-hash-table)))
(for-each (lambda (elem)
- (apply hash-set! table elem))
- elems)
+ (apply hash-set! table elem))
+ elems)
table)))
(define (animal->family animal)
@cindex SRFI-11
@findex let-values
-@findex let-values*
+@findex let*-values
This module implements the binding forms for multiple values
-@code{let-values} and @code{let-values*}. These forms are similar to
+@code{let-values} and @code{let*-values}. These forms are similar to
@code{let} and @code{let*} (@pxref{Local Bindings}), but they support
binding of the values returned by multiple-valued expressions.
@code{let-values} performs all bindings simultaneously, which means that
no expression in the binding clauses may refer to variables bound in the
-same clause list. @code{let-values*}, on the other hand, performs the
+same clause list. @code{let*-values}, on the other hand, performs the
bindings sequentially, just like @code{let*} does for single-valued
expressions.
@cindex variable arity
@cindex arity, variable
-@c FIXME::martin: Review me!
+SRFI-16 defines a variable-arity @code{lambda} form,
+@code{case-lambda}. This form is available in the default Guile
+environment. @xref{Case-lambda}, for more information.
-@findex case-lambda
-The syntactic form @code{case-lambda} creates procedures, just like
-@code{lambda}, but has syntactic extensions for writing procedures of
-varying arity easier.
+@node SRFI-17
+@subsection SRFI-17 - Generalized set!
+@cindex SRFI-17
-The syntax of the @code{case-lambda} form is defined in the following
-EBNF grammar.
+This SRFI implements a generalized @code{set!}, allowing some
+``referencing'' functions to be used as the target location of a
+@code{set!}. This feature is available from
@example
-@group
-<case-lambda>
- --> (case-lambda <case-lambda-clause>)
-<case-lambda-clause>
- --> (<formals> <definition-or-command>*)
-<formals>
- --> (<identifier>*)
- | (<identifier>* . <identifier>)
- | <identifier>
-@end group
+(use-modules (srfi srfi-17))
@end example
-The value returned by a @code{case-lambda} form is a procedure which
-matches the number of actual arguments against the formals in the
-various clauses, in order. @dfn{Formals} means a formal argument list
-just like with @code{lambda} (@pxref{Lambda}). The first matching clause
-is selected, the corresponding values from the actual parameter list are
-bound to the variable names in the clauses and the body of the clause is
-evaluated. If no clause matches, an error is signalled.
-
-The following (silly) definition creates a procedure @var{foo} which
-acts differently, depending on the number of actual arguments. If one
-argument is given, the constant @code{#t} is returned, two arguments are
-added and if more arguments are passed, their product is calculated.
-
-@lisp
-(define foo (case-lambda
- ((x) #t)
- ((x y) (+ x y))
- (z
- (apply * z))))
-(foo 'bar)
-@result{}
-#t
-(foo 2 4)
-@result{}
-6
-(foo 3 3 3)
-@result{}
-27
-(foo)
-@result{}
-1
-@end lisp
-
-The last expression evaluates to 1 because the last clause is matched,
-@var{z} is bound to the empty list and the following multiplication,
-applied to zero arguments, yields 1.
-
+@noindent
+For example @code{vector-ref} is extended so that
-@node SRFI-17
-@subsection SRFI-17 - Generalized set!
-@cindex SRFI-17
+@example
+(set! (vector-ref vec idx) new-value)
+@end example
-This is an implementation of SRFI-17: Generalized set!
+@noindent
+is equivalent to
-@findex getter-with-setter
-It exports the Guile procedure @code{make-procedure-with-setter} under
-the SRFI name @code{getter-with-setter} and exports the standard
-procedures @code{car}, @code{cdr}, @dots{}, @code{cdddr},
-@code{string-ref} and @code{vector-ref} as procedures with setters, as
-required by the SRFI.
+@example
+(vector-set! vec idx new-value)
+@end example
-SRFI-17 was heavily criticized during its discussion period but it was
-finalized anyway. One issue was its concept of globally associating
-setter @dfn{properties} with (procedure) values, which is non-Schemy.
-For this reason, this implementation chooses not to provide a way to set
-the setter of a procedure. In fact, @code{(set! (setter @var{proc})
-@var{setter})} signals an error. The only way to attach a setter to a
-procedure is to create a new object (a @dfn{procedure with setter}) via
-the @code{getter-with-setter} procedure. This procedure is also
-specified in the SRFI. Using it avoids the described problems.
+The idea is that a @code{vector-ref} expression identifies a location,
+which may be either fetched or stored. The same form is used for the
+location in both cases, encouraging visual clarity. This is similar
+to the idea of an ``lvalue'' in C.
+
+The mechanism for this kind of @code{set!} is in the Guile core
+(@pxref{Procedures with Setters}). This module adds definitions of
+the following functions as procedures with setters, allowing them to
+be targets of a @code{set!},
+
+@quotation
+@nicode{car}, @nicode{cdr}, @nicode{caar}, @nicode{cadr},
+@nicode{cdar}, @nicode{cddr}, @nicode{caaar}, @nicode{caadr},
+@nicode{cadar}, @nicode{caddr}, @nicode{cdaar}, @nicode{cdadr},
+@nicode{cddar}, @nicode{cdddr}, @nicode{caaaar}, @nicode{caaadr},
+@nicode{caadar}, @nicode{caaddr}, @nicode{cadaar}, @nicode{cadadr},
+@nicode{caddar}, @nicode{cadddr}, @nicode{cdaaar}, @nicode{cdaadr},
+@nicode{cdadar}, @nicode{cdaddr}, @nicode{cddaar}, @nicode{cddadr},
+@nicode{cdddar}, @nicode{cddddr}
+
+@nicode{string-ref}, @nicode{vector-ref}
+@end quotation
+
+The SRFI specifies @code{setter} (@pxref{Procedures with Setters}) as
+a procedure with setter, allowing the setter for a procedure to be
+changed, eg.@: @code{(set! (setter foo) my-new-setter-handler)}.
+Currently Guile does not implement this, a setter can only be
+specified on creation (@code{getter-with-setter} below).
+
+@defun getter-with-setter
+The same as the Guile core @code{make-procedure-with-setter}
+(@pxref{Procedures with Setters}).
+@end defun
-@node SRFI-19
-@subsection SRFI-19 - Time/Date Library
-@cindex SRFI-19
-@cindex time
-@cindex date
+@node SRFI-18
+@subsection SRFI-18 - Multithreading support
+@cindex SRFI-18
-This is an implementation of the SRFI-19 time/date library. The
-functions and variables described here are provided by
+This is an implementation of the SRFI-18 threading and synchronization
+library. The functions and variables described here are provided by
@example
-(use-modules (srfi srfi-19))
+(use-modules (srfi srfi-18))
@end example
+As a general rule, the data types and functions in this SRFI-18
+implementation are compatible with the types and functions in Guile's
+core threading code. For example, mutexes created with the SRFI-18
+@code{make-mutex} function can be passed to the built-in Guile
+function @code{lock-mutex} (@pxref{Mutexes and Condition Variables}),
+and mutexes created with the built-in Guile function @code{make-mutex}
+can be passed to the SRFI-18 function @code{mutex-lock!}. Cases in
+which this does not hold true are noted in the following sections.
+
@menu
-* SRFI-19 Introduction::
-* SRFI-19 Time::
-* SRFI-19 Date::
-* SRFI-19 Time/Date conversions::
-* SRFI-19 Date to string::
-* SRFI-19 String to date::
+* SRFI-18 Threads:: Executing code
+* SRFI-18 Mutexes:: Mutual exclusion devices
+* SRFI-18 Condition variables:: Synchronizing of groups of threads
+* SRFI-18 Time:: Representation of times and durations
+* SRFI-18 Exceptions:: Signalling and handling errors
@end menu
-@node SRFI-19 Introduction
-@subsubsection SRFI-19 Introduction
+@node SRFI-18 Threads
+@subsubsection SRFI-18 Threads
+
+Threads created by SRFI-18 differ in two ways from threads created by
+Guile's built-in thread functions. First, a thread created by SRFI-18
+@code{make-thread} begins in a blocked state and will not start
+execution until @code{thread-start!} is called on it. Second, SRFI-18
+threads are constructed with a top-level exception handler that
+captures any exceptions that are thrown on thread exit. In all other
+regards, SRFI-18 threads are identical to normal Guile threads.
+
+@defun current-thread
+Returns the thread that called this function. This is the same
+procedure as the same-named built-in procedure @code{current-thread}
+(@pxref{Threads}).
+@end defun
-@cindex universal time
-@cindex atomic time
-@cindex UTC
-@cindex TAI
-This module implements time and date representations and calculations,
-in various time systems, including universal time (UTC) and atomic
-time (TAI).
+@defun thread? obj
+Returns @code{#t} if @var{obj} is a thread, @code{#f} otherwise. This
+is the same procedure as the same-named built-in procedure
+@code{thread?} (@pxref{Threads}).
+@end defun
-For those not familiar with these time systems, TAI is based on a
-fixed length second derived from oscillations of certain atoms. UTC
-differs from TAI by an integral number of seconds, which is increased
-or decreased at announced times to keep UTC aligned to a mean solar
-day (the orbit and rotation of the earth are not quite constant).
+@defun make-thread thunk [name]
+Call @code{thunk} in a new thread and with a new dynamic state,
+returning the new thread and optionally assigning it the object name
+@var{name}, which may be any Scheme object.
-@cindex leap second
-So far, only increases in the TAI
-@tex
+Note that the name @code{make-thread} conflicts with the
+@code{(ice-9 threads)} function @code{make-thread}. Applications
+wanting to use both of these functions will need to refer to them by
+different names.
+@end defun
+
+@defun thread-name thread
+Returns the name assigned to @var{thread} at the time of its creation,
+or @code{#f} if it was not given a name.
+@end defun
+
+@defun thread-specific thread
+@defunx thread-specific-set! thread obj
+Get or set the ``object-specific'' property of @var{thread}. In
+Guile's implementation of SRFI-18, this value is stored as an object
+property, and will be @code{#f} if not set.
+@end defun
+
+@defun thread-start! thread
+Unblocks @var{thread} and allows it to begin execution if it has not
+done so already.
+@end defun
+
+@defun thread-yield!
+If one or more threads are waiting to execute, calling
+@code{thread-yield!} forces an immediate context switch to one of them.
+Otherwise, @code{thread-yield!} has no effect. @code{thread-yield!}
+behaves identically to the Guile built-in function @code{yield}.
+@end defun
+
+@defun thread-sleep! timeout
+The current thread waits until the point specified by the time object
+@var{timeout} is reached (@pxref{SRFI-18 Time}). This blocks the
+thread only if @var{timeout} represents a point in the future. it is
+an error for @var{timeout} to be @code{#f}.
+@end defun
+
+@defun thread-terminate! thread
+Causes an abnormal termination of @var{thread}. If @var{thread} is
+not already terminated, all mutexes owned by @var{thread} become
+unlocked/abandoned. If @var{thread} is the current thread,
+@code{thread-terminate!} does not return. Otherwise
+@code{thread-terminate!} returns an unspecified value; the termination
+of @var{thread} will occur before @code{thread-terminate!} returns.
+Subsequent attempts to join on @var{thread} will cause a ``terminated
+thread exception'' to be raised.
+
+@code{thread-terminate!} is compatible with the thread cancellation
+procedures in the core threads API (@pxref{Threads}) in that if a
+cleanup handler has been installed for the target thread, it will be
+called before the thread exits and its return value (or exception, if
+any) will be stored for later retrieval via a call to
+@code{thread-join!}.
+@end defun
+
+@defun thread-join! thread [timeout [timeout-val]]
+Wait for @var{thread} to terminate and return its exit value. When a
+time value @var{timeout} is given, it specifies a point in time where
+the waiting should be aborted. When the waiting is aborted,
+@var{timeoutval} is returned if it is specified; otherwise, a
+@code{join-timeout-exception} exception is raised
+(@pxref{SRFI-18 Exceptions}). Exceptions may also be raised if the
+thread was terminated by a call to @code{thread-terminate!}
+(@code{terminated-thread-exception} will be raised) or if the thread
+exited by raising an exception that was handled by the top-level
+exception handler (@code{uncaught-exception} will be raised; the
+original exception can be retrieved using
+@code{uncaught-exception-reason}).
+@end defun
+
+
+@node SRFI-18 Mutexes
+@subsubsection SRFI-18 Mutexes
+
+The behavior of Guile's built-in mutexes is parameterized via a set of
+flags passed to the @code{make-mutex} procedure in the core
+(@pxref{Mutexes and Condition Variables}). To satisfy the requirements
+for mutexes specified by SRFI-18, the @code{make-mutex} procedure
+described below sets the following flags:
+@itemize @bullet
+@item
+@code{recursive}: the mutex can be locked recursively
+@item
+@code{unchecked-unlock}: attempts to unlock a mutex that is already
+unlocked will not raise an exception
+@item
+@code{allow-external-unlock}: the mutex can be unlocked by any thread,
+not just the thread that locked it originally
+@end itemize
+
+@defun make-mutex [name]
+Returns a new mutex, optionally assigning it the object name
+@var{name}, which may be any Scheme object. The returned mutex will be
+created with the configuration described above. Note that the name
+@code{make-mutex} conflicts with Guile core function @code{make-mutex}.
+Applications wanting to use both of these functions will need to refer
+to them by different names.
+@end defun
+
+@defun mutex-name mutex
+Returns the name assigned to @var{mutex} at the time of its creation,
+or @code{#f} if it was not given a name.
+@end defun
+
+@defun mutex-specific mutex
+@defunx mutex-specific-set! mutex obj
+Get or set the ``object-specific'' property of @var{mutex}. In Guile's
+implementation of SRFI-18, this value is stored as an object property,
+and will be @code{#f} if not set.
+@end defun
+
+@defun mutex-state mutex
+Returns information about the state of @var{mutex}. Possible values
+are:
+@itemize @bullet
+@item
+thread @code{T}: the mutex is in the locked/owned state and thread T
+is the owner of the mutex
+@item
+symbol @code{not-owned}: the mutex is in the locked/not-owned state
+@item
+symbol @code{abandoned}: the mutex is in the unlocked/abandoned state
+@item
+symbol @code{not-abandoned}: the mutex is in the
+unlocked/not-abandoned state
+@end itemize
+@end defun
+
+@defun mutex-lock! mutex [timeout [thread]]
+Lock @var{mutex}, optionally specifying a time object @var{timeout}
+after which to abort the lock attempt and a thread @var{thread} giving
+a new owner for @var{mutex} different than the current thread. This
+procedure has the same behavior as the @code{lock-mutex} procedure in
+the core library.
+@end defun
+
+@defun mutex-unlock! mutex [condition-variable [timeout]]
+Unlock @var{mutex}, optionally specifying a condition variable
+@var{condition-variable} on which to wait, either indefinitely or,
+optionally, until the time object @var{timeout} has passed, to be
+signalled. This procedure has the same behavior as the
+@code{unlock-mutex} procedure in the core library.
+@end defun
+
+
+@node SRFI-18 Condition variables
+@subsubsection SRFI-18 Condition variables
+
+SRFI-18 does not specify a ``wait'' function for condition variables.
+Waiting on a condition variable can be simulated using the SRFI-18
+@code{mutex-unlock!} function described in the previous section, or
+Guile's built-in @code{wait-condition-variable} procedure can be used.
+
+@defun condition-variable? obj
+Returns @code{#t} if @var{obj} is a condition variable, @code{#f}
+otherwise. This is the same procedure as the same-named built-in
+procedure
+(@pxref{Mutexes and Condition Variables, @code{condition-variable?}}).
+@end defun
+
+@defun make-condition-variable [name]
+Returns a new condition variable, optionally assigning it the object
+name @var{name}, which may be any Scheme object. This procedure
+replaces a procedure of the same name in the core library.
+@end defun
+
+@defun condition-variable-name condition-variable
+Returns the name assigned to @var{thread} at the time of its creation,
+or @code{#f} if it was not given a name.
+@end defun
+
+@defun condition-variable-specific condition-variable
+@defunx condition-variable-specific-set! condition-variable obj
+Get or set the ``object-specific'' property of
+@var{condition-variable}. In Guile's implementation of SRFI-18, this
+value is stored as an object property, and will be @code{#f} if not
+set.
+@end defun
+
+@defun condition-variable-signal! condition-variable
+@defunx condition-variable-broadcast! condition-variable
+Wake up one thread that is waiting for @var{condition-variable}, in
+the case of @code{condition-variable-signal!}, or all threads waiting
+for it, in the case of @code{condition-variable-broadcast!}. The
+behavior of these procedures is equivalent to that of the procedures
+@code{signal-condition-variable} and
+@code{broadcast-condition-variable} in the core library.
+@end defun
+
+
+@node SRFI-18 Time
+@subsubsection SRFI-18 Time
+
+The SRFI-18 time functions manipulate time in two formats: a
+``time object'' type that represents an absolute point in time in some
+implementation-specific way; and the number of seconds since some
+unspecified ``epoch''. In Guile's implementation, the epoch is the
+Unix epoch, 00:00:00 UTC, January 1, 1970.
+
+@defun current-time
+Return the current time as a time object. This procedure replaces
+the procedure of the same name in the core library, which returns the
+current time in seconds since the epoch.
+@end defun
+
+@defun time? obj
+Returns @code{#t} if @var{obj} is a time object, @code{#f} otherwise.
+@end defun
+
+@defun time->seconds time
+@defunx seconds->time seconds
+Convert between time objects and numerical values representing the
+number of seconds since the epoch. When converting from a time object
+to seconds, the return value is the number of seconds between
+@var{time} and the epoch. When converting from seconds to a time
+object, the return value is a time object that represents a time
+@var{seconds} seconds after the epoch.
+@end defun
+
+
+@node SRFI-18 Exceptions
+@subsubsection SRFI-18 Exceptions
+
+SRFI-18 exceptions are identical to the exceptions provided by
+Guile's implementation of SRFI-34. The behavior of exception
+handlers invoked to handle exceptions thrown from SRFI-18 functions,
+however, differs from the conventional behavior of SRFI-34 in that
+the continuation of the handler is the same as that of the call to
+the function. Handlers are called in a tail-recursive manner; the
+exceptions do not ``bubble up''.
+
+@defun current-exception-handler
+Returns the current exception handler.
+@end defun
+
+@defun with-exception-handler handler thunk
+Installs @var{handler} as the current exception handler and calls the
+procedure @var{thunk} with no arguments, returning its value as the
+value of the exception. @var{handler} must be a procedure that accepts
+a single argument. The current exception handler at the time this
+procedure is called will be restored after the call returns.
+@end defun
+
+@defun raise obj
+Raise @var{obj} as an exception. This is the same procedure as the
+same-named procedure defined in SRFI 34.
+@end defun
+
+@defun join-timeout-exception? obj
+Returns @code{#t} if @var{obj} is an exception raised as the result of
+performing a timed join on a thread that does not exit within the
+specified timeout, @code{#f} otherwise.
+@end defun
+
+@defun abandoned-mutex-exception? obj
+Returns @code{#t} if @var{obj} is an exception raised as the result of
+attempting to lock a mutex that has been abandoned by its owner thread,
+@code{#f} otherwise.
+@end defun
+
+@defun terminated-thread-exception? obj
+Returns @code{#t} if @var{obj} is an exception raised as the result of
+joining on a thread that exited as the result of a call to
+@code{thread-terminate!}.
+@end defun
+
+@defun uncaught-exception? obj
+@defunx uncaught-exception-reason exc
+@code{uncaught-exception?} returns @code{#t} if @var{obj} is an
+exception thrown as the result of joining a thread that exited by
+raising an exception that was handled by the top-level exception
+handler installed by @code{make-thread}. When this occurs, the
+original exception is preserved as part of the exception thrown by
+@code{thread-join!} and can be accessed by calling
+@code{uncaught-exception-reason} on that exception. Note that
+because this exception-preservation mechanism is a side-effect of
+@code{make-thread}, joining on threads that exited as described above
+but were created by other means will not raise this
+@code{uncaught-exception} error.
+@end defun
+
+
+@node SRFI-19
+@subsection SRFI-19 - Time/Date Library
+@cindex SRFI-19
+@cindex time
+@cindex date
+
+This is an implementation of the SRFI-19 time/date library. The
+functions and variables described here are provided by
+
+@example
+(use-modules (srfi srfi-19))
+@end example
+
+@strong{Caution}: The current code in this module incorrectly extends
+the Gregorian calendar leap year rule back prior to the introduction
+of those reforms in 1582 (or the appropriate year in various
+countries). The Julian calendar was used prior to 1582, and there
+were 10 days skipped for the reform, but the code doesn't implement
+that.
+
+This will be fixed some time. Until then calculations for 1583
+onwards are correct, but prior to that any day/month/year and day of
+the week calculations are wrong.
+
+@menu
+* SRFI-19 Introduction::
+* SRFI-19 Time::
+* SRFI-19 Date::
+* SRFI-19 Time/Date conversions::
+* SRFI-19 Date to string::
+* SRFI-19 String to date::
+@end menu
+
+@node SRFI-19 Introduction
+@subsubsection SRFI-19 Introduction
+
+@cindex universal time
+@cindex atomic time
+@cindex UTC
+@cindex TAI
+This module implements time and date representations and calculations,
+in various time systems, including universal time (UTC) and atomic
+time (TAI).
+
+For those not familiar with these time systems, TAI is based on a
+fixed length second derived from oscillations of certain atoms. UTC
+differs from TAI by an integral number of seconds, which is increased
+or decreased at announced times to keep UTC aligned to a mean solar
+day (the orbit and rotation of the earth are not quite constant).
+
+@cindex leap second
+So far, only increases in the TAI
+@tex
$\leftrightarrow$
@end tex
@ifnottex
@var{type} is @code{time-utc}.
Note that the name @code{current-time} conflicts with the Guile core
-@code{current-time} function (@pxref{Time}). Applications wanting to
-use both will need to use a different name for one of them.
+@code{current-time} function (@pxref{Time}) as well as the SRFI-18
+@code{current-time} function (@pxref{SRFI-18 Time}). Applications
+wanting to use more than one of these functions will need to refer to
+them by different names.
@end defun
@defun time-resolution [type]
instance @code{time-tai->time-utc} accepts a @var{time} object of type
@code{time-tai} and returns an object of type @code{time-utc}.
-For conversions to dates, @var{tz-offset} is seconds east of
-Greenwich. The default is the local timezone, at the given time, as
-provided by the system.
-
The @code{!} variants may modify their @var{time} argument to form
their return. The plain functions create a new object.
+
+For conversions to dates, @var{tz-offset} is seconds east of
+Greenwich. The default is the local timezone, at the given time, as
+provided by the system, using @code{localtime} (@pxref{Time}).
+
+On 32-bit systems, @code{localtime} is limited to a 32-bit
+@code{time_t}, so a default @var{tz-offset} is only available for
+times between Dec 1901 and Jan 2038. For prior dates an application
+might like to use the value in 1902, though some locations have zone
+changes prior to that. For future dates an application might like to
+assume today's rules extend indefinitely. But for correct daylight
+savings transitions it will be necessary to take an offset for the
+same day and time but a year in range and which has the same starting
+weekday and same leap/non-leap (to support rules like last Sunday in
+October).
@end defun
@node SRFI-19 Date to string
described here, since the specification and reference implementation
differ.
-Currently Guile doesn't implement any localizations for the above, all
-outputs are in English, and the @samp{~c} conversion is POSIX
-@code{ctime} style @samp{~a ~b ~d ~H:~M:~S~z ~Y}. This may change in
-the future.
+Conversion is locale-dependent on systems that support it
+(@pxref{Accessing Locale Information}). @xref{Locales,
+@code{setlocale}}, for information on how to change the current
+locale.
@node SRFI-19 String to date
@cindex date, from string
@c FIXME: Can we say what happens when an incomplete date is
-@c converted? Ie. fields left as 0, or what? The spec seems to be
+@c converted? I.e. fields left as 0, or what? The spec seems to be
@c silent on this.
@defun string->date input template
returned, instead the weekday will be derived from the day, month and
year.
-Currently Guile doesn't implement any localizations for the above,
-month and weekday names are always expected in English. This may
-change in the future.
+Conversion is locale-dependent on systems that support it
+(@pxref{Accessing Locale Information}). @xref{Locales,
+@code{setlocale}}, for information on how to change the current
+locale.
@end defun
+@node SRFI-23
+@subsection SRFI-23 - Error Reporting
+@cindex SRFI-23
+
+The SRFI-23 @code{error} procedure is always available.
@node SRFI-26
@subsection SRFI-26 - specializing parameters
@end example
@end deffn
+@node SRFI-27
+@subsection SRFI-27 - Sources of Random Bits
+@cindex SRFI-27
+
+This subsection is based on the
+@uref{http://srfi.schemers.org/srfi-27/srfi-27.html, specification of
+SRFI-27} written by Sebastian Egner.
+
+@c The copyright notice and license text of the SRFI-27 specification is
+@c reproduced below:
+
+@c Copyright (C) Sebastian Egner (2002). All Rights Reserved.
+
+@c Permission is hereby granted, free of charge, to any person obtaining a
+@c copy of this software and associated documentation files (the
+@c "Software"), to deal in the Software without restriction, including
+@c without limitation the rights to use, copy, modify, merge, publish,
+@c distribute, sublicense, and/or sell copies of the Software, and to
+@c permit persons to whom the Software is furnished to do so, subject to
+@c the following conditions:
+
+@c The above copyright notice and this permission notice shall be included
+@c in all copies or substantial portions of the Software.
+
+@c THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+@c OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+@c MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+@c NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+@c LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+@c OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+@c WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+This SRFI provides access to a (pseudo) random number generator; for
+Guile's built-in random number facilities, which SRFI-27 is implemented
+upon, @xref{Random}. With SRFI-27, random numbers are obtained from a
+@emph{random source}, which encapsulates a random number generation
+algorithm and its state.
+
+@menu
+* SRFI-27 Default Random Source:: Obtaining random numbers
+* SRFI-27 Random Sources:: Creating and manipulating random sources
+* SRFI-27 Random Number Generators:: Obtaining random number generators
+@end menu
+
+@node SRFI-27 Default Random Source
+@subsubsection The Default Random Source
+@cindex SRFI-27
+
+@defun random-integer n
+Return a random number between zero (inclusive) and @var{n} (exclusive),
+using the default random source. The numbers returned have a uniform
+distribution.
+@end defun
+
+@defun random-real
+Return a random number in (0,1), using the default random source. The
+numbers returned have a uniform distribution.
+@end defun
+
+@defun default-random-source
+A random source from which @code{random-integer} and @code{random-real}
+have been derived using @code{random-source-make-integers} and
+@code{random-source-make-reals} (@pxref{SRFI-27 Random Number Generators}
+for those procedures). Note that an assignment to
+@code{default-random-source} does not change @code{random-integer} or
+@code{random-real}; it is also strongly recommended not to assign a new
+value.
+@end defun
+
+@node SRFI-27 Random Sources
+@subsubsection Random Sources
+@cindex SRFI-27
+
+@defun make-random-source
+Create a new random source. The stream of random numbers obtained from
+each random source created by this procedure will be identical, unless
+its state is changed by one of the procedures below.
+@end defun
+
+@defun random-source? object
+Tests whether @var{object} is a random source. Random sources are a
+disjoint type.
+@end defun
+
+@defun random-source-randomize! source
+Attempt to set the state of the random source to a truly random value.
+The current implementation uses a seed based on the current system time.
+@end defun
+
+@defun random-source-pseudo-randomize! source i j
+Changes the state of the random source s into the initial state of the
+(@var{i}, @var{j})-th independent random source, where @var{i} and
+@var{j} are non-negative integers. This procedure provides a mechanism
+to obtain a large number of independent random sources (usually all
+derived from the same backbone generator), indexed by two integers. In
+contrast to @code{random-source-randomize!}, this procedure is entirely
+deterministic.
+@end defun
+
+The state associated with a random state can be obtained an reinstated
+with the following procedures:
+
+@defun random-source-state-ref source
+@defunx random-source-state-set! source state
+Get and set the state of a random source. No assumptions should be made
+about the nature of the state object, besides it having an external
+representation (i.e.@: it can be passed to @code{write} and subsequently
+@code{read} back).
+@end defun
+
+@node SRFI-27 Random Number Generators
+@subsubsection Obtaining random number generator procedures
+@cindex SRFI-27
+
+@defun random-source-make-integers source
+Obtains a procedure to generate random integers using the random source
+@var{source}. The returned procedure takes a single argument @var{n},
+which must be a positive integer, and returns the next uniformly
+distributed random integer from the interval @{0, ..., @var{n}-1@} by
+advancing the state of @var{source}.
+
+If an application obtains and uses several generators for the same
+random source @var{source}, a call to any of these generators advances
+the state of @var{source}. Hence, the generators do not produce the
+same sequence of random integers each but rather share a state. This
+also holds for all other types of generators derived from a fixed random
+sources.
+
+While the SRFI text specifies that ``Implementations that support
+concurrency make sure that the state of a generator is properly
+advanced'', this is currently not the case in Guile's implementation of
+SRFI-27, as it would cause a severe performance penalty. So in
+multi-threaded programs, you either must perform locking on random
+sources shared between threads yourself, or use different random sources
+for multiple threads.
+@end defun
+
+@defun random-source-make-reals source
+@defunx random-source-make-reals source unit
+Obtains a procedure to generate random real numbers @math{0 < x < 1}
+using the random source @var{source}. The procedure rand is called
+without arguments.
+
+The optional parameter @var{unit} determines the type of numbers being
+produced by the returned procedure and the quantization of the output.
+@var{unit} must be a number such that @math{0 < @var{unit} < 1}. The
+numbers created by the returned procedure are of the same numerical type
+as @var{unit} and the potential output values are spaced by at most
+@var{unit}. One can imagine rand to create numbers as @var{x} *
+@var{unit} where @var{x} is a random integer in @{1, ...,
+floor(1/unit)-1@}. Note, however, that this need not be the way the
+values are actually created and that the actual resolution of rand can
+be much higher than unit. In case @var{unit} is absent it defaults to a
+reasonably small value (related to the width of the mantissa of an
+efficient number format).
+@end defun
+
+@node SRFI-30
+@subsection SRFI-30 - Nested Multi-line Comments
+@cindex SRFI-30
+
+Starting from version 2.0, Guile's @code{read} supports SRFI-30/R6RS
+nested multi-line comments by default, @ref{Block Comments}.
+
@node SRFI-31
@subsection SRFI-31 - A special form `rec' for recursive evaluation
@cindex SRFI-31
guile>
@end lisp
+
+@node SRFI-34
+@subsection SRFI-34 - Exception handling for programs
+
+@cindex SRFI-34
+Guile provides an implementation of
+@uref{http://srfi.schemers.org/srfi-34/srfi-34.html, SRFI-34's exception
+handling mechanisms} as an alternative to its own built-in mechanisms
+(@pxref{Exceptions}). It can be made available as follows:
+
+@lisp
+(use-modules (srfi srfi-34))
+@end lisp
+
+@c FIXME: Document it.
+
+
+@node SRFI-35
+@subsection SRFI-35 - Conditions
+
+@cindex SRFI-35
+@cindex conditions
+@cindex exceptions
+
+@uref{http://srfi.schemers.org/srfi-35/srfi-35.html, SRFI-35} implements
+@dfn{conditions}, a data structure akin to records designed to convey
+information about exceptional conditions between parts of a program. It
+is normally used in conjunction with SRFI-34's @code{raise}:
+
+@lisp
+(raise (condition (&message
+ (message "An error occurred"))))
+@end lisp
+
+Users can define @dfn{condition types} containing arbitrary information.
+Condition types may inherit from one another. This allows the part of
+the program that handles (or ``catches'') conditions to get accurate
+information about the exceptional condition that arose.
+
+SRFI-35 conditions are made available using:
+
+@lisp
+(use-modules (srfi srfi-35))
+@end lisp
+
+The procedures available to manipulate condition types are the
+following:
+
+@deffn {Scheme Procedure} make-condition-type id parent field-names
+Return a new condition type named @var{id}, inheriting from
+@var{parent}, and with the fields whose names are listed in
+@var{field-names}. @var{field-names} must be a list of symbols and must
+not contain names already used by @var{parent} or one of its supertypes.
+@end deffn
+
+@deffn {Scheme Procedure} condition-type? obj
+Return true if @var{obj} is a condition type.
+@end deffn
+
+Conditions can be created and accessed with the following procedures:
+
+@deffn {Scheme Procedure} make-condition type . field+value
+Return a new condition of type @var{type} with fields initialized as
+specified by @var{field+value}, a sequence of field names (symbols) and
+values as in the following example:
+
+@lisp
+(let ((&ct (make-condition-type 'foo &condition '(a b c))))
+ (make-condition &ct 'a 1 'b 2 'c 3))
+@end lisp
+
+Note that all fields of @var{type} and its supertypes must be specified.
+@end deffn
+
+@deffn {Scheme Procedure} make-compound-condition . conditions
+Return a new compound condition composed of @var{conditions}. The
+returned condition has the type of each condition of @var{conditions}
+(per @code{condition-has-type?}).
+@end deffn
+
+@deffn {Scheme Procedure} condition-has-type? c type
+Return true if condition @var{c} has type @var{type}.
+@end deffn
+
+@deffn {Scheme Procedure} condition-ref c field-name
+Return the value of the field named @var{field-name} from condition @var{c}.
+
+If @var{c} is a compound condition and several underlying condition
+types contain a field named @var{field-name}, then the value of the
+first such field is returned, using the order in which conditions were
+passed to @var{make-compound-condition}.
+@end deffn
+
+@deffn {Scheme Procedure} extract-condition c type
+Return a condition of condition type @var{type} with the field values
+specified by @var{c}.
+
+If @var{c} is a compound condition, extract the field values from the
+subcondition belonging to @var{type} that appeared first in the call to
+@code{make-compound-condition} that created the condition.
+@end deffn
+
+Convenience macros are also available to create condition types and
+conditions.
+
+@deffn {library syntax} define-condition-type type supertype predicate field-spec...
+Define a new condition type named @var{type} that inherits from
+@var{supertype}. In addition, bind @var{predicate} to a type predicate
+that returns true when passed a condition of type @var{type} or any of
+its subtypes. @var{field-spec} must have the form @code{(field
+accessor)} where @var{field} is the name of field of @var{type} and
+@var{accessor} is the name of a procedure to access field @var{field} in
+conditions of type @var{type}.
+
+The example below defines condition type @code{&foo}, inheriting from
+@code{&condition} with fields @code{a}, @code{b} and @code{c}:
+
+@lisp
+(define-condition-type &foo &condition
+ foo-condition?
+ (a foo-a)
+ (b foo-b)
+ (c foo-c))
+@end lisp
+@end deffn
+
+@deffn {library syntax} condition type-field-bindings...
+Return a new condition, or compound condition, initialized according to
+@var{type-field-bindings}. Each @var{type-field-binding} must have the
+form @code{(type field-specs...)}, where @var{type} is the name of a
+variable bound to condition type; each @var{field-spec} must have the
+form @code{(field-name value)} where @var{field-name} is a symbol
+denoting the field being initialized to @var{value}. As for
+@code{make-condition}, all fields must be specified.
+
+The following example returns a simple condition:
+
+@lisp
+(condition (&message (message "An error occurred")))
+@end lisp
+
+The one below returns a compound condition:
+
+@lisp
+(condition (&message (message "An error occurred"))
+ (&serious))
+@end lisp
+@end deffn
+
+Finally, SRFI-35 defines a several standard condition types.
+
+@defvar &condition
+This condition type is the root of all condition types. It has no
+fields.
+@end defvar
+
+@defvar &message
+A condition type that carries a message describing the nature of the
+condition to humans.
+@end defvar
+
+@deffn {Scheme Procedure} message-condition? c
+Return true if @var{c} is of type @code{&message} or one of its
+subtypes.
+@end deffn
+
+@deffn {Scheme Procedure} condition-message c
+Return the message associated with message condition @var{c}.
+@end deffn
+
+@defvar &serious
+This type describes conditions serious enough that they cannot safely be
+ignored. It has no fields.
+@end defvar
+
+@deffn {Scheme Procedure} serious-condition? c
+Return true if @var{c} is of type @code{&serious} or one of its
+subtypes.
+@end deffn
+
+@defvar &error
+This condition describes errors, typically caused by something that has
+gone wrong in the interaction of the program with the external world or
+the user.
+@end defvar
+
+@deffn {Scheme Procedure} error? c
+Return true if @var{c} is of type @code{&error} or one of its subtypes.
+@end deffn
+
+@node SRFI-37
+@subsection SRFI-37 - args-fold
+@cindex SRFI-37
+
+This is a processor for GNU @code{getopt_long}-style program
+arguments. It provides an alternative, less declarative interface
+than @code{getopt-long} in @code{(ice-9 getopt-long)}
+(@pxref{getopt-long,,The (ice-9 getopt-long) Module}). Unlike
+@code{getopt-long}, it supports repeated options and any number of
+short and long names per option. Access it with:
+
+@lisp
+(use-modules (srfi srfi-37))
+@end lisp
+
+@acronym{SRFI}-37 principally provides an @code{option} type and the
+@code{args-fold} function. To use the library, create a set of
+options with @code{option} and use it as a specification for invoking
+@code{args-fold}.
+
+Here is an example of a simple argument processor for the typical
+@samp{--version} and @samp{--help} options, which returns a backwards
+list of files given on the command line:
+
+@lisp
+(args-fold (cdr (program-arguments))
+ (let ((display-and-exit-proc
+ (lambda (msg)
+ (lambda (opt name arg loads)
+ (display msg) (quit)))))
+ (list (option '(#\v "version") #f #f
+ (display-and-exit-proc "Foo version 42.0\n"))
+ (option '(#\h "help") #f #f
+ (display-and-exit-proc
+ "Usage: foo scheme-file ..."))))
+ (lambda (opt name arg loads)
+ (error "Unrecognized option `~A'" name))
+ (lambda (op loads) (cons op loads))
+ '())
+@end lisp
+
+@deffn {Scheme Procedure} option names required-arg? optional-arg? processor
+Return an object that specifies a single kind of program option.
+
+@var{names} is a list of command-line option names, and should consist of
+characters for traditional @code{getopt} short options and strings for
+@code{getopt_long}-style long options.
+
+@var{required-arg?} and @var{optional-arg?} are mutually exclusive;
+one or both must be @code{#f}. If @var{required-arg?}, the option
+must be followed by an argument on the command line, such as
+@samp{--opt=value} for long options, or an error will be signalled.
+If @var{optional-arg?}, an argument will be taken if available.
+
+@var{processor} is a procedure that takes at least 3 arguments, called
+when @code{args-fold} encounters the option: the containing option
+object, the name used on the command line, and the argument given for
+the option (or @code{#f} if none). The rest of the arguments are
+@code{args-fold} ``seeds'', and the @var{processor} should return
+seeds as well.
+@end deffn
+
+@deffn {Scheme Procedure} option-names opt
+@deffnx {Scheme Procedure} option-required-arg? opt
+@deffnx {Scheme Procedure} option-optional-arg? opt
+@deffnx {Scheme Procedure} option-processor opt
+Return the specified field of @var{opt}, an option object, as
+described above for @code{option}.
+@end deffn
+
+@deffn {Scheme Procedure} args-fold args options unrecognized-option-proc operand-proc seeds @dots{}
+Process @var{args}, a list of program arguments such as that returned
+by @code{(cdr (program-arguments))}, in order against @var{options}, a
+list of option objects as described above. All functions called take
+the ``seeds'', or the last multiple-values as multiple arguments,
+starting with @var{seeds}, and must return the new seeds. Return the
+final seeds.
+
+Call @code{unrecognized-option-proc}, which is like an option object's
+processor, for any options not found in @var{options}.
+
+Call @code{operand-proc} with any items on the command line that are
+not named options. This includes arguments after @samp{--}. It is
+called with the argument in question, as well as the seeds.
+@end deffn
+
+@node SRFI-38
+@subsection SRFI-38 - External Representation for Data With Shared Structure
+@cindex SRFI-38
+
+This subsection is based on
+@uref{http://srfi.schemers.org/srfi-38/srfi-38.html, the specification
+of SRFI-38} written by Ray Dillinger.
+
+@c Copyright (C) Ray Dillinger 2003. All Rights Reserved.
+
+@c Permission is hereby granted, free of charge, to any person obtaining a
+@c copy of this software and associated documentation files (the
+@c "Software"), to deal in the Software without restriction, including
+@c without limitation the rights to use, copy, modify, merge, publish,
+@c distribute, sublicense, and/or sell copies of the Software, and to
+@c permit persons to whom the Software is furnished to do so, subject to
+@c the following conditions:
+
+@c The above copyright notice and this permission notice shall be included
+@c in all copies or substantial portions of the Software.
+
+@c THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+@c OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+@c MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+@c NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+@c LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+@c OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+@c WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+This SRFI creates an alternative external representation for data
+written and read using @code{write-with-shared-structure} and
+@code{read-with-shared-structure}. It is identical to the grammar for
+external representation for data written and read with @code{write} and
+@code{read} given in section 7 of R5RS, except that the single
+production
+
+@example
+<datum> --> <simple datum> | <compound datum>
+@end example
+
+is replaced by the following five productions:
+
+@example
+<datum> --> <defining datum> | <nondefining datum> | <defined datum>
+<defining datum> --> #<indexnum>=<nondefining datum>
+<defined datum> --> #<indexnum>#
+<nondefining datum> --> <simple datum> | <compound datum>
+<indexnum> --> <digit 10>+
+@end example
+
+@deffn {Scheme procedure} write-with-shared-structure obj
+@deffnx {Scheme procedure} write-with-shared-structure obj port
+@deffnx {Scheme procedure} write-with-shared-structure obj port optarg
+
+Writes an external representation of @var{obj} to the given port.
+Strings that appear in the written representation are enclosed in
+doublequotes, and within those strings backslash and doublequote
+characters are escaped by backslashes. Character objects are written
+using the @code{#\} notation.
+
+Objects which denote locations rather than values (cons cells, vectors,
+and non-zero-length strings in R5RS scheme; also Guile's structs,
+bytevectors and ports and hash-tables), if they appear at more than one
+point in the data being written, are preceded by @samp{#@var{N}=} the
+first time they are written and replaced by @samp{#@var{N}#} all
+subsequent times they are written, where @var{N} is a natural number
+used to identify that particular object. If objects which denote
+locations occur only once in the structure, then
+@code{write-with-shared-structure} must produce the same external
+representation for those objects as @code{write}.
+
+@code{write-with-shared-structure} terminates in finite time and
+produces a finite representation when writing finite data.
+
+@code{write-with-shared-structure} returns an unspecified value. The
+@var{port} argument may be omitted, in which case it defaults to the
+value returned by @code{(current-output-port)}. The @var{optarg}
+argument may also be omitted. If present, its effects on the output and
+return value are unspecified but @code{write-with-shared-structure} must
+still write a representation that can be read by
+@code{read-with-shared-structure}. Some implementations may wish to use
+@var{optarg} to specify formatting conventions, numeric radixes, or
+return values. Guile's implementation ignores @var{optarg}.
+
+For example, the code
+
+@lisp
+(begin (define a (cons 'val1 'val2))
+ (set-cdr! a a)
+ (write-with-shared-structure a))
+@end lisp
+
+should produce the output @code{#1=(val1 . #1#)}. This shows a cons
+cell whose @code{cdr} contains itself.
+
+@end deffn
+
+@deffn {Scheme procedure} read-with-shared-structure
+@deffnx {Scheme procedure} read-with-shared-structure port
+
+@code{read-with-shared-structure} converts the external representations
+of Scheme objects produced by @code{write-with-shared-structure} into
+Scheme objects. That is, it is a parser for the nonterminal
+@samp{<datum>} in the augmented external representation grammar defined
+above. @code{read-with-shared-structure} returns the next object
+parsable from the given input port, updating @var{port} to point to the
+first character past the end of the external representation of the
+object.
+
+If an end-of-file is encountered in the input before any characters are
+found that can begin an object, then an end-of-file object is returned.
+The port remains open, and further attempts to read it (by
+@code{read-with-shared-structure} or @code{read} will also return an
+end-of-file object. If an end of file is encountered after the
+beginning of an object's external representation, but the external
+representation is incomplete and therefore not parsable, an error is
+signalled.
+
+The @var{port} argument may be omitted, in which case it defaults to the
+value returned by @code{(current-input-port)}. It is an error to read
+from a closed port.
+
+@end deffn
+
+@node SRFI-39
+@subsection SRFI-39 - Parameters
+@cindex SRFI-39
+@cindex parameter object
+@tindex Parameter
+
+This SRFI provides parameter objects, which implement dynamically
+bound locations for values. The functions below are available from
+
+@example
+(use-modules (srfi srfi-39))
+@end example
+
+A parameter object is a procedure. Called with no arguments it
+returns its value, called with one argument it sets the value.
+
+@example
+(define my-param (make-parameter 123))
+(my-param) @result{} 123
+(my-param 456)
+(my-param) @result{} 456
+@end example
+
+The @code{parameterize} special form establishes new locations for
+parameters, those new locations having effect within the dynamic scope
+of the @code{parameterize} body. Leaving restores the previous
+locations, or re-entering through a saved continuation will again use
+the new locations.
+
+@example
+(parameterize ((my-param 789))
+ (my-param) @result{} 789
+ )
+(my-param) @result{} 456
+@end example
+
+Parameters are like dynamically bound variables in other Lisp dialects.
+They allow an application to establish parameter settings (as the name
+suggests) just for the execution of a particular bit of code,
+restoring when done. Examples of such parameters might be
+case-sensitivity for a search, or a prompt for user input.
+
+Global variables are not as good as parameter objects for this sort of
+thing. Changes to them are visible to all threads, but in Guile
+parameter object locations are per-thread, thereby truly limiting the
+effect of @code{parameterize} to just its dynamic execution.
+
+Passing arguments to functions is thread-safe, but that soon becomes
+tedious when there's more than a few or when they need to pass down
+through several layers of calls before reaching the point they should
+affect. And introducing a new setting to existing code is often
+easier with a parameter object than adding arguments.
+
+
+@sp 1
+@defun make-parameter init [converter]
+Return a new parameter object, with initial value @var{init}.
+
+A parameter object is a procedure. When called @code{(param)} it
+returns its value, or a call @code{(param val)} sets its value. For
+example,
+
+@example
+(define my-param (make-parameter 123))
+(my-param) @result{} 123
+
+(my-param 456)
+(my-param) @result{} 456
+@end example
+
+If a @var{converter} is given, then a call @code{(@var{converter}
+val)} is made for each value set, its return is the value stored.
+Such a call is made for the @var{init} initial value too.
+
+A @var{converter} allows values to be validated, or put into a
+canonical form. For example,
+
+@example
+(define my-param (make-parameter 123
+ (lambda (val)
+ (if (not (number? val))
+ (error "must be a number"))
+ (inexact->exact val))))
+(my-param 0.75)
+(my-param) @result{} 3/4
+@end example
+@end defun
+
+@deffn {library syntax} parameterize ((param value) @dots{}) body @dots{}
+Establish a new dynamic scope with the given @var{param}s bound to new
+locations and set to the given @var{value}s. @var{body} is evaluated
+in that environment, the result is the return from the last form in
+@var{body}.
+
+Each @var{param} is an expression which is evaluated to get the
+parameter object. Often this will just be the name of a variable
+holding the object, but it can be anything that evaluates to a
+parameter.
+
+The @var{param} expressions and @var{value} expressions are all
+evaluated before establishing the new dynamic bindings, and they're
+evaluated in an unspecified order.
+
+For example,
+
+@example
+(define prompt (make-parameter "Type something: "))
+(define (get-input)
+ (display (prompt))
+ ...)
+
+(parameterize ((prompt "Type a number: "))
+ (get-input)
+ ...)
+@end example
+@end deffn
+
+@deffn {Parameter object} current-input-port [new-port]
+@deffnx {Parameter object} current-output-port [new-port]
+@deffnx {Parameter object} current-error-port [new-port]
+This SRFI extends the core @code{current-input-port} and
+@code{current-output-port}, making them parameter objects. The
+Guile-specific @code{current-error-port} is extended too, for
+consistency. (@pxref{Default Ports}.)
+
+This is an upwardly compatible extension, a plain call like
+@code{(current-input-port)} still returns the current input port, and
+@code{set-current-input-port} can still be used. But the port can now
+also be set with @code{(current-input-port my-port)} and bound
+dynamically with @code{parameterize}.
+@end deffn
+
+@defun with-parameters* param-list value-list thunk
+Establish a new dynamic scope, as per @code{parameterize} above,
+taking parameters from @var{param-list} and corresponding values from
+@var{values-list}. A call @code{(@var{thunk})} is made in the new
+scope and the result from that @var{thunk} is the return from
+@code{with-parameters*}.
+
+This function is a Guile-specific addition to the SRFI, it's similar
+to the core @code{with-fluids*} (@pxref{Fluids and Dynamic States}).
+@end defun
+
+
+@sp 1
+Parameter objects are implemented using fluids (@pxref{Fluids and
+Dynamic States}), so each dynamic state has it's own parameter
+locations. That includes the separate locations when outside any
+@code{parameterize} form. When a parameter is created it gets a
+separate initial location in each dynamic state, all initialized to
+the given @var{init} value.
+
+As alluded to above, because each thread usually has a separate
+dynamic state, each thread has it's own locations behind parameter
+objects, and changes in one thread are not visible to any other. When
+a new dynamic state or thread is created, the values of parameters in
+the originating context are copied, into new locations.
+
+SRFI-39 doesn't specify the interaction between parameter objects and
+threads, so the threading behaviour described here should be regarded
+as Guile-specific.
+
+@node SRFI-42
+@subsection SRFI-42 - Eager Comprehensions
+@cindex SRFI-42
+
+See @uref{http://srfi.schemers.org/srfi-42/srfi-42.html, the
+specification of SRFI-42}.
+
+@node SRFI-45
+@subsection SRFI-45 - Primitives for Expressing Iterative Lazy Algorithms
+@cindex SRFI-45
+
+This subsection is based on @uref{http://srfi.schemers.org/srfi-45/srfi-45.html, the
+specification of SRFI-45} written by Andr@'e van Tonder.
+
+@c Copyright (C) André van Tonder (2003). All Rights Reserved.
+
+@c Permission is hereby granted, free of charge, to any person obtaining a
+@c copy of this software and associated documentation files (the
+@c "Software"), to deal in the Software without restriction, including
+@c without limitation the rights to use, copy, modify, merge, publish,
+@c distribute, sublicense, and/or sell copies of the Software, and to
+@c permit persons to whom the Software is furnished to do so, subject to
+@c the following conditions:
+
+@c The above copyright notice and this permission notice shall be included
+@c in all copies or substantial portions of the Software.
+
+@c THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+@c OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+@c MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+@c NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+@c LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+@c OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+@c WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+Lazy evaluation is traditionally simulated in Scheme using @code{delay}
+and @code{force}. However, these primitives are not powerful enough to
+express a large class of lazy algorithms that are iterative. Indeed, it
+is folklore in the Scheme community that typical iterative lazy
+algorithms written using delay and force will often require unbounded
+memory.
+
+This SRFI provides set of three operations: @{@code{lazy}, @code{delay},
+@code{force}@}, which allow the programmer to succinctly express lazy
+algorithms while retaining bounded space behavior in cases that are
+properly tail-recursive. A general recipe for using these primitives is
+provided. An additional procedure @code{eager} is provided for the
+construction of eager promises in cases where efficiency is a concern.
+
+Although this SRFI redefines @code{delay} and @code{force}, the
+extension is conservative in the sense that the semantics of the subset
+@{@code{delay}, @code{force}@} in isolation (i.e., as long as the
+program does not use @code{lazy}) agrees with that in R5RS. In other
+words, no program that uses the R5RS definitions of delay and force will
+break if those definition are replaced by the SRFI-45 definitions of
+delay and force.
+
+@deffn {Scheme Syntax} delay expression
+Takes an expression of arbitrary type @var{a} and returns a promise of
+type @code{(Promise @var{a})} which at some point in the future may be
+asked (by the @code{force} procedure) to evaluate the expression and
+deliver the resulting value.
+@end deffn
+
+@deffn {Scheme Syntax} lazy expression
+Takes an expression of type @code{(Promise @var{a})} and returns a
+promise of type @code{(Promise @var{a})} which at some point in the
+future may be asked (by the @code{force} procedure) to evaluate the
+expression and deliver the resulting promise.
+@end deffn
+
+@deffn {Scheme Procedure} force expression
+Takes an argument of type @code{(Promise @var{a})} and returns a value
+of type @var{a} as follows: If a value of type @var{a} has been computed
+for the promise, this value is returned. Otherwise, the promise is
+first evaluated, then overwritten by the obtained promise or value, and
+then force is again applied (iteratively) to the promise.
+@end deffn
+
+@deffn {Scheme Procedure} eager expression
+Takes an argument of type @var{a} and returns a value of type
+@code{(Promise @var{a})}. As opposed to @code{delay}, the argument is
+evaluated eagerly. Semantically, writing @code{(eager expression)} is
+equivalent to writing
+
+@lisp
+(let ((value expression)) (delay value)).
+@end lisp
+
+However, the former is more efficient since it does not require
+unnecessary creation and evaluation of thunks. We also have the
+equivalence
+
+@lisp
+(delay expression) = (lazy (eager expression))
+@end lisp
+@end deffn
+
+The following reduction rules may be helpful for reasoning about these
+primitives. However, they do not express the memoization and memory
+usage semantics specified above:
+
+@lisp
+(force (delay expression)) -> expression
+(force (lazy expression)) -> (force expression)
+(force (eager value)) -> value
+@end lisp
+
+@subsubheading Correct usage
+
+We now provide a general recipe for using the primitives @{@code{lazy},
+@code{delay}, @code{force}@} to express lazy algorithms in Scheme. The
+transformation is best described by way of an example: Consider the
+stream-filter algorithm, expressed in a hypothetical lazy language as
+
+@lisp
+(define (stream-filter p? s)
+ (if (null? s) '()
+ (let ((h (car s))
+ (t (cdr s)))
+ (if (p? h)
+ (cons h (stream-filter p? t))
+ (stream-filter p? t)))))
+@end lisp
+
+This algorithm can be expressed as follows in Scheme:
+
+@lisp
+(define (stream-filter p? s)
+ (lazy
+ (if (null? (force s)) (delay '())
+ (let ((h (car (force s)))
+ (t (cdr (force s))))
+ (if (p? h)
+ (delay (cons h (stream-filter p? t)))
+ (stream-filter p? t))))))
+@end lisp
+
+In other words, we
+
+@itemize @bullet
+@item
+wrap all constructors (e.g., @code{'()}, @code{cons}) with @code{delay},
+@item
+apply @code{force} to arguments of deconstructors (e.g., @code{car},
+@code{cdr} and @code{null?}),
+@item
+wrap procedure bodies with @code{(lazy ...)}.
+@end itemize
+
+@node SRFI-55
+@subsection SRFI-55 - Requiring Features
+@cindex SRFI-55
+
+SRFI-55 provides @code{require-extension} which is a portable
+mechanism to load selected SRFI modules. This is implemented in the
+Guile core, there's no module needed to get SRFI-55 itself.
+
+@deffn {library syntax} require-extension clause@dots{}
+Require each of the given @var{clause} features, throwing an error if
+any are unavailable.
+
+A @var{clause} is of the form @code{(@var{identifier} arg...)}. The
+only @var{identifier} currently supported is @code{srfi} and the
+arguments are SRFI numbers. For example to get SRFI-1 and SRFI-6,
+
+@example
+(require-extension (srfi 1 6))
+@end example
+
+@code{require-extension} can only be used at the top-level.
+
+A Guile-specific program can simply @code{use-modules} to load SRFIs
+not already in the core, @code{require-extension} is for programs
+designed to be portable to other Scheme implementations.
+@end deffn
+
+
+@node SRFI-60
+@subsection SRFI-60 - Integers as Bits
+@cindex SRFI-60
+@cindex integers as bits
+@cindex bitwise logical
+
+This SRFI provides various functions for treating integers as bits and
+for bitwise manipulations. These functions can be obtained with,
+
+@example
+(use-modules (srfi srfi-60))
+@end example
+
+Integers are treated as infinite precision twos-complement, the same
+as in the core logical functions (@pxref{Bitwise Operations}). And
+likewise bit indexes start from 0 for the least significant bit. The
+following functions in this SRFI are already in the Guile core,
+
+@quotation
+@code{logand},
+@code{logior},
+@code{logxor},
+@code{lognot},
+@code{logtest},
+@code{logcount},
+@code{integer-length},
+@code{logbit?},
+@code{ash}
+@end quotation
+
+@sp 1
+@defun bitwise-and n1 ...
+@defunx bitwise-ior n1 ...
+@defunx bitwise-xor n1 ...
+@defunx bitwise-not n
+@defunx any-bits-set? j k
+@defunx bit-set? index n
+@defunx arithmetic-shift n count
+@defunx bit-field n start end
+@defunx bit-count n
+Aliases for @code{logand}, @code{logior}, @code{logxor},
+@code{lognot}, @code{logtest}, @code{logbit?}, @code{ash},
+@code{bit-extract} and @code{logcount} respectively.
+
+Note that the name @code{bit-count} conflicts with @code{bit-count} in
+the core (@pxref{Bit Vectors}).
+@end defun
+
+@defun bitwise-if mask n1 n0
+@defunx bitwise-merge mask n1 n0
+Return an integer with bits selected from @var{n1} and @var{n0}
+according to @var{mask}. Those bits where @var{mask} has 1s are taken
+from @var{n1}, and those where @var{mask} has 0s are taken from
+@var{n0}.
+
+@example
+(bitwise-if 3 #b0101 #b1010) @result{} 9
+@end example
+@end defun
+
+@defun log2-binary-factors n
+@defunx first-set-bit n
+Return a count of how many factors of 2 are present in @var{n}. This
+is also the bit index of the lowest 1 bit in @var{n}. If @var{n} is
+0, the return is @math{-1}.
+
+@example
+(log2-binary-factors 6) @result{} 1
+(log2-binary-factors -8) @result{} 3
+@end example
+@end defun
+
+@defun copy-bit index n newbit
+Return @var{n} with the bit at @var{index} set according to
+@var{newbit}. @var{newbit} should be @code{#t} to set the bit to 1,
+or @code{#f} to set it to 0. Bits other than at @var{index} are
+unchanged in the return.
+
+@example
+(copy-bit 1 #b0101 #t) @result{} 7
+@end example
+@end defun
+
+@defun copy-bit-field n newbits start end
+Return @var{n} with the bits from @var{start} (inclusive) to @var{end}
+(exclusive) changed to the value @var{newbits}.
+
+The least significant bit in @var{newbits} goes to @var{start}, the
+next to @math{@var{start}+1}, etc. Anything in @var{newbits} past the
+@var{end} given is ignored.
+
+@example
+(copy-bit-field #b10000 #b11 1 3) @result{} #b10110
+@end example
+@end defun
+
+@defun rotate-bit-field n count start end
+Return @var{n} with the bit field from @var{start} (inclusive) to
+@var{end} (exclusive) rotated upwards by @var{count} bits.
+
+@var{count} can be positive or negative, and it can be more than the
+field width (it'll be reduced modulo the width).
+
+@example
+(rotate-bit-field #b0110 2 1 4) @result{} #b1010
+@end example
+@end defun
+
+@defun reverse-bit-field n start end
+Return @var{n} with the bits from @var{start} (inclusive) to @var{end}
+(exclusive) reversed.
+
+@example
+(reverse-bit-field #b101001 2 4) @result{} #b100101
+@end example
+@end defun
+
+@defun integer->list n [len]
+Return bits from @var{n} in the form of a list of @code{#t} for 1 and
+@code{#f} for 0. The least significant @var{len} bits are returned,
+and the first list element is the most significant of those bits. If
+@var{len} is not given, the default is @code{(integer-length @var{n})}
+(@pxref{Bitwise Operations}).
+
+@example
+(integer->list 6) @result{} (#t #t #f)
+(integer->list 1 4) @result{} (#f #f #f #t)
+@end example
+@end defun
+
+@defun list->integer lst
+@defunx booleans->integer bool@dots{}
+Return an integer formed bitwise from the given @var{lst} list of
+booleans, or for @code{booleans->integer} from the @var{bool}
+arguments.
+
+Each boolean is @code{#t} for a 1 and @code{#f} for a 0. The first
+element becomes the most significant bit in the return.
+
+@example
+(list->integer '(#t #f #t #f)) @result{} 10
+@end example
+@end defun
+
+
+@node SRFI-61
+@subsection SRFI-61 - A more general @code{cond} clause
+
+This SRFI extends RnRS @code{cond} to support test expressions that
+return multiple values, as well as arbitrary definitions of test
+success. SRFI 61 is implemented in the Guile core; there's no module
+needed to get SRFI-61 itself. Extended @code{cond} is documented in
+@ref{if cond case,, Simple Conditional Evaluation}.
+
+@node SRFI-67
+@subsection SRFI-67 - Compare procedures
+@cindex SRFI-67
+
+See @uref{http://srfi.schemers.org/srfi-67/srfi-67.html, the
+specification of SRFI-67}.
+
+@node SRFI-69
+@subsection SRFI-69 - Basic hash tables
+@cindex SRFI-69
+
+This is a portable wrapper around Guile's built-in hash table and weak
+table support. @xref{Hash Tables}, for information on that built-in
+support. Above that, this hash-table interface provides association
+of equality and hash functions with tables at creation time, so
+variants of each function are not required, as well as a procedure
+that takes care of most uses for Guile hash table handles, which this
+SRFI does not provide as such.
+
+Access it with:
+
+@lisp
+(use-modules (srfi srfi-69))
+@end lisp
+
+@menu
+* SRFI-69 Creating hash tables::
+* SRFI-69 Accessing table items::
+* SRFI-69 Table properties::
+* SRFI-69 Hash table algorithms::
+@end menu
+
+@node SRFI-69 Creating hash tables
+@subsubsection Creating hash tables
+
+@deffn {Scheme Procedure} make-hash-table [equal-proc hash-proc #:weak weakness start-size]
+Create and answer a new hash table with @var{equal-proc} as the
+equality function and @var{hash-proc} as the hashing function.
+
+By default, @var{equal-proc} is @code{equal?}. It can be any
+two-argument procedure, and should answer whether two keys are the
+same for this table's purposes.
+
+My default @var{hash-proc} assumes that @code{equal-proc} is no
+coarser than @code{equal?} unless it is literally @code{string-ci=?}.
+If provided, @var{hash-proc} should be a two-argument procedure that
+takes a key and the current table size, and answers a reasonably good
+hash integer between 0 (inclusive) and the size (exclusive).
+
+@var{weakness} should be @code{#f} or a symbol indicating how ``weak''
+the hash table is:
+
+@table @code
+@item #f
+An ordinary non-weak hash table. This is the default.
+
+@item key
+When the key has no more non-weak references at GC, remove that entry.
+
+@item value
+When the value has no more non-weak references at GC, remove that
+entry.
+
+@item key-or-value
+When either has no more non-weak references at GC, remove the
+association.
+@end table
+
+As a legacy of the time when Guile couldn't grow hash tables,
+@var{start-size} is an optional integer argument that specifies the
+approximate starting size for the hash table, which will be rounded to
+an algorithmically-sounder number.
+@end deffn
+
+By @dfn{coarser} than @code{equal?}, we mean that for all @var{x} and
+@var{y} values where @code{(@var{equal-proc} @var{x} @var{y})},
+@code{(equal? @var{x} @var{y})} as well. If that does not hold for
+your @var{equal-proc}, you must provide a @var{hash-proc}.
+
+In the case of weak tables, remember that @dfn{references} above
+always refers to @code{eq?}-wise references. Just because you have a
+reference to some string @code{"foo"} doesn't mean that an association
+with key @code{"foo"} in a weak-key table @emph{won't} be collected;
+it only counts as a reference if the two @code{"foo"}s are @code{eq?},
+regardless of @var{equal-proc}. As such, it is usually only sensible
+to use @code{eq?} and @code{hashq} as the equivalence and hash
+functions for a weak table. @xref{Weak References}, for more
+information on Guile's built-in weak table support.
+
+@deffn {Scheme Procedure} alist->hash-table alist [equal-proc hash-proc #:weak weakness start-size]
+As with @code{make-hash-table}, but initialize it with the
+associations in @var{alist}. Where keys are repeated in @var{alist},
+the leftmost association takes precedence.
+@end deffn
+
+@node SRFI-69 Accessing table items
+@subsubsection Accessing table items
+
+@deffn {Scheme Procedure} hash-table-ref table key [default-thunk]
+@deffnx {Scheme Procedure} hash-table-ref/default table key default
+Answer the value associated with @var{key} in @var{table}. If
+@var{key} is not present, answer the result of invoking the thunk
+@var{default-thunk}, which signals an error instead by default.
+
+@code{hash-table-ref/default} is a variant that requires a third
+argument, @var{default}, and answers @var{default} itself instead of
+invoking it.
+@end deffn
+
+@deffn {Scheme Procedure} hash-table-set! table key new-value
+Set @var{key} to @var{new-value} in @var{table}.
+@end deffn
+
+@deffn {Scheme Procedure} hash-table-delete! table key
+Remove the association of @var{key} in @var{table}, if present. If
+absent, do nothing.
+@end deffn
+
+@deffn {Scheme Procedure} hash-table-exists? table key
+Answer whether @var{key} has an association in @var{table}.
+@end deffn
+
+@deffn {Scheme Procedure} hash-table-update! table key modifier [default-thunk]
+@deffnx {Scheme Procedure} hash-table-update!/default table key modifier default
+Replace @var{key}'s associated value in @var{table} by invoking
+@var{modifier} with one argument, the old value.
+
+If @var{key} is not present, and @var{default-thunk} is provided,
+invoke it with no arguments to get the ``old value'' to be passed to
+@var{modifier} as above. If @var{default-thunk} is not provided in
+such a case, signal an error.
+
+@code{hash-table-update!/default} is a variant that requires the
+fourth argument, which is used directly as the ``old value'' rather
+than as a thunk to be invoked to retrieve the ``old value''.
+@end deffn
+
+@node SRFI-69 Table properties
+@subsubsection Table properties
+
+@deffn {Scheme Procedure} hash-table-size table
+Answer the number of associations in @var{table}. This is guaranteed
+to run in constant time for non-weak tables.
+@end deffn
+
+@deffn {Scheme Procedure} hash-table-keys table
+Answer an unordered list of the keys in @var{table}.
+@end deffn
+
+@deffn {Scheme Procedure} hash-table-values table
+Answer an unordered list of the values in @var{table}.
+@end deffn
+
+@deffn {Scheme Procedure} hash-table-walk table proc
+Invoke @var{proc} once for each association in @var{table}, passing
+the key and value as arguments.
+@end deffn
+
+@deffn {Scheme Procedure} hash-table-fold table proc init
+Invoke @code{(@var{proc} @var{key} @var{value} @var{previous})} for
+each @var{key} and @var{value} in @var{table}, where @var{previous} is
+the result of the previous invocation, using @var{init} as the first
+@var{previous} value. Answer the final @var{proc} result.
+@end deffn
+
+@deffn {Scheme Procedure} hash-table->alist table
+Answer an alist where each association in @var{table} is an
+association in the result.
+@end deffn
+
+@node SRFI-69 Hash table algorithms
+@subsubsection Hash table algorithms
+
+Each hash table carries an @dfn{equivalence function} and a @dfn{hash
+function}, used to implement key lookups. Beginning users should
+follow the rules for consistency of the default @var{hash-proc}
+specified above. Advanced users can use these to implement their own
+equivalence and hash functions for specialized lookup semantics.
+
+@deffn {Scheme Procedure} hash-table-equivalence-function hash-table
+@deffnx {Scheme Procedure} hash-table-hash-function hash-table
+Answer the equivalence and hash function of @var{hash-table}, respectively.
+@end deffn
+
+@deffn {Scheme Procedure} hash obj [size]
+@deffnx {Scheme Procedure} string-hash obj [size]
+@deffnx {Scheme Procedure} string-ci-hash obj [size]
+@deffnx {Scheme Procedure} hash-by-identity obj [size]
+Answer a hash value appropriate for equality predicate @code{equal?},
+@code{string=?}, @code{string-ci=?}, and @code{eq?}, respectively.
+@end deffn
+
+@code{hash} is a backwards-compatible replacement for Guile's built-in
+@code{hash}.
+
+@node SRFI-88
+@subsection SRFI-88 Keyword Objects
+@cindex SRFI-88
+@cindex keyword objects
+
+@uref{http://srfi.schemers.org/srfi-88/srfi-88.html, SRFI-88} provides
+@dfn{keyword objects}, which are equivalent to Guile's keywords
+(@pxref{Keywords}). SRFI-88 keywords can be entered using the
+@dfn{postfix keyword syntax}, which consists of an identifier followed
+by @code{:} (@pxref{Scheme Read, @code{postfix} keyword syntax}).
+SRFI-88 can be made available with:
+
+@example
+(use-modules (srfi srfi-88))
+@end example
+
+Doing so installs the right reader option for keyword syntax, using
+@code{(read-set! keywords 'postfix)}. It also provides the procedures
+described below.
+
+@deffn {Scheme Procedure} keyword? obj
+Return @code{#t} if @var{obj} is a keyword. This is the same procedure
+as the same-named built-in procedure (@pxref{Keyword Procedures,
+@code{keyword?}}).
+
+@example
+(keyword? foo:) @result{} #t
+(keyword? 'foo:) @result{} #t
+(keyword? "foo") @result{} #f
+@end example
+@end deffn
+
+@deffn {Scheme Procedure} keyword->string kw
+Return the name of @var{kw} as a string, i.e., without the trailing
+colon. The returned string may not be modified, e.g., with
+@code{string-set!}.
+
+@example
+(keyword->string foo:) @result{} "foo"
+@end example
+@end deffn
+
+@deffn {Scheme Procedure} string->keyword str
+Return the keyword object whose name is @var{str}.
+
+@example
+(keyword->string (string->keyword "a b c")) @result{} "a b c"
+@end example
+@end deffn
+
+@node SRFI-98
+@subsection SRFI-98 Accessing environment variables.
+@cindex SRFI-98
+@cindex environment variables
+
+This is a portable wrapper around Guile's built-in support for
+interacting with the current environment, @xref{Runtime Environment}.
+
+@deffn {Scheme Procedure} get-environment-variable name
+Returns a string containing the value of the environment variable
+given by the string @code{name}, or @code{#f} if the named
+environment variable is not found. This is equivalent to
+@code{(getenv name)}.
+@end deffn
+
+@deffn {Scheme Procedure} get-environment-variables
+Returns the names and values of all the environment variables as an
+association list in which both the keys and the values are strings.
+@end deffn
+
@c srfi-modules.texi ends here
@c Local Variables:
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