@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1998 Free Software Foundation, Inc.
+@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1998, 1999
+@c Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@setfilename ../info/streams
@node Read and Print, Minibuffers, Debugging, Top
text produces a list (but not the same list) with elements @code{a}
and @code{b}.
- However, these two operations are not precisely inverses. There are
-three kinds of exceptions:
+ However, these two operations are not precisely inverse to each other.
+There are three kinds of exceptions:
@itemize @bullet
@item
@code{t} used as a stream means that the input is read from the
minibuffer. In fact, the minibuffer is invoked once and the text
given by the user is made into a string that is then used as the
-input stream.
+input stream. If Emacs is running in batch mode, standard input is used
+instead of the minibuffer. For example,
+@example
+(message "%s" (read t))
+@end example
+will read a Lisp expression from standard input and print the result
+to standard output.
@item @code{nil}
@cindex @code{nil} input stream
points into, at the marker position. The marker position advances as
characters are inserted. The value of point in the buffer has no effect
on printing when the stream is a marker, and this kind of printing
-does not move point.
+does not move point (except that if the marker points at or before the
+position of point, point advances with the surrounding text, as
+usual).
@item @var{function}
@cindex function output stream
@group
last-output
- @result{} (10 34 116 117 112 116 117 111 32 101 104
+ @result{} (10 34 116 117 112 116 117 111 32 101 104
116 32 115 105 32 115 105 104 84 34 10)
@end group
@end example
(progn (print 'The\ cat\ in)
(print "the hat")
(print " came back"))
- @print{}
+ @print{}
@print{} The\ cat\ in
- @print{}
+ @print{}
@print{} "the hat"
- @print{}
+ @print{}
@print{} " came back"
- @print{}
+ @print{}
@result{} " came back"
@end group
@end example
@example
@group
-(progn (prin1 'The\ cat\ in)
- (prin1 "the hat")
+(progn (prin1 'The\ cat\ in)
+ (prin1 "the hat")
(prin1 " came back"))
@print{} The\ cat\ in"the hat"" came back"
@result{} " came back"
@end defun
@defmac with-output-to-string body...
-@tindex with-output-to-string
This macro executes the @var{body} forms with @code{standard-output} set
up to feed output into a string. Then it returns that string.
that print functions use when the @var{stream} argument is @code{nil}.
@end defvar
+@defvar print-quoted
+If this is non-@code{nil}, that means to print quoted forms using
+abbreviated reader syntax. @code{(quote foo)} prints as @code{'foo},
+@code{(function foo)} as @code{#'foo}, and backquoted forms print
+using modern backquote syntax.
+@end defvar
+
@defvar print-escape-newlines
@cindex @samp{\n} in print
@cindex escape characters
@code{prin1}, but not during the printing of the result.
@end defvar
-@tindex print-escape-nonascii
@defvar print-escape-nonascii
-If this variable is non-@code{nil}, then unibyte non-@sc{ascii}
+If this variable is non-@code{nil}, then unibyte non-@acronym{ASCII}
characters in strings are unconditionally printed as backslash sequences
by the print functions @code{prin1} and @code{print} that print with
quoting.
-Those functions also use backslash sequences for unibyte non-@sc{ascii}
+Those functions also use backslash sequences for unibyte non-@acronym{ASCII}
characters, regardless of the value of this variable, when the output
stream is a multibyte buffer or a marker pointing into one.
@end defvar
-@tindex print-escape-multibyte
@defvar print-escape-multibyte
-If this variable is non-@code{nil}, then multibyte non-@sc{ascii}
+If this variable is non-@code{nil}, then multibyte non-@acronym{ASCII}
characters in strings are unconditionally printed as backslash sequences
by the print functions @code{prin1} and @code{print} that print with
quoting.
Those functions also use backslash sequences for multibyte
-non-@sc{ascii} characters, regardless of the value of this variable,
+non-@acronym{ASCII} characters, regardless of the value of this variable,
when the output stream is a unibyte buffer or a marker pointing into
one.
@end defvar
@code{nil} (which is the default) means no limit.
@end defvar
- These variables are used for detecting and reporting circular
+@defopt eval-expression-print-length
+@defoptx eval-expression-print-level
+These are the values for @code{print-length} and @code{print-level}
+used by @code{eval-expression}, and thus, indirectly, by many
+interactive evaluation commands (@pxref{Lisp Eval,, Evaluating
+Emacs-Lisp Expressions, emacs, The GNU Emacs Manual}).
+@end defopt
+
+ These variables are used for detecting and reporting circular
and shared structure---but they are only defined in Emacs 21.
@tindex print-circle
@defvar print-circle
-If non-@code{nil}, this variable enables detection of circular
+If non-@code{nil}, this variable enables detection of circular
and shared structure in printing.
@end defvar
reader to produce an uninterned symbol.
@end defvar
-@tindex print-continuous-numbering
@defvar print-continuous-numbering
-To print several objects with shared structure in common, you should
-bind @code{print-continuous-numbering} to @code{t} around them all.
-That tells @code{print} not to reinitialize @code{print-number-table}
-each time.
+If non-@code{nil}, that means number continuously across print calls.
+This affects the numbers printed for @samp{#@var{n}=} labels and
+@samp{#@var{m}#} references.
+
+Don't set this variable with @code{setq}; you should only bind it
+temporarily to @code{t} with @code{let}. When you do that, you should
+also bind @code{print-number-table} to @code{nil}.
@end defvar
-@tindex print-number-table
@defvar print-number-table
-This variable holds the table used as the basis of outputting
-@samp{#@var{n}=} and @samp{#@var{n}#} constructs for circular and shared
-structure. When you want to print several objects with shared structure
-in common, you should bind @code{print-number-table} to @code{nil}
-around them all.
+This variable holds a vector used internally by printing to implement
+the @code{print-circle} feature. You should not use it except
+to bind it to @code{nil} when you bind @code{print-continuous-numbering}.
@end defvar
- Here is an example of printing two objects with a common
-set of shared substructure:
+@defvar float-output-format
+This variable specifies how to print floating point numbers. Its
+default value is @code{nil}, meaning use the shortest output
+that represents the number without losing information.
-@example
-(let ((print-circle t)
- (print-continuous-numbering t)
- print-number-table)
- (print1 x)
- (print1 y))
-@end example
+To control output format more precisely, you can put a string in this
+variable. The string should hold a @samp{%}-specification to be used
+in the C function @code{sprintf}. For further restrictions on what
+you can use, see the variable's documentation string.
+@end defvar
+
+@ignore
+ arch-tag: 07636b8c-c4e3-4735-9e06-2e864320b434
+@end ignore
HCoop / bpt / emacs.git / blobdiff