diff options
author | Andy Wingo <wingo@pobox.com> | 2009-12-29 13:26:41 +0100 |
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committer | Andy Wingo <wingo@pobox.com> | 2009-12-29 13:29:02 +0100 |
commit | b8596c08ac2ef2201c1e8559ac5f4d62ebde3d91 (patch) | |
tree | 962bf49500208df34beb7665a71259fc9f521af4 /doc/ref/misc-modules.texi | |
parent | 8c6eea2f1a6fab2d2be4d0de6a6826273eb2c3c9 (diff) | |
download | guile-b8596c08ac2ef2201c1e8559ac5f4d62ebde3d91.tar.gz |
add ~@y truncated printing directive to format
* doc/ref/misc-modules.texi (Formatted Output): Add documentation for
the new ~@y format directive.
(Pretty Printing): Add documentation for truncated-write.
* module/ice-9/format.scm (format): Add ~@y, for doing a truncated
print. Also, allow both ~y variants to take a width parameter.
Diffstat (limited to 'doc/ref/misc-modules.texi')
-rw-r--r-- | doc/ref/misc-modules.texi | 75 |
1 files changed, 71 insertions, 4 deletions
diff --git a/doc/ref/misc-modules.texi b/doc/ref/misc-modules.texi index 28a636f26..1449292cd 100644 --- a/doc/ref/misc-modules.texi +++ b/doc/ref/misc-modules.texi @@ -1,6 +1,6 @@ @c -*-texinfo-*- @c This is part of the GNU Guile Reference Manual. -@c Copyright (C) 1996, 1997, 2000, 2001, 2002, 2003, 2004, 2006 +@c Copyright (C) 1996, 1997, 2000, 2001, 2002, 2003, 2004, 2006, 2009 @c Free Software Foundation, Inc. @c See the file guile.texi for copying conditions. @@ -16,7 +16,7 @@ The module @code{(ice-9 pretty-print)} provides the procedure objects. This is especially useful for deeply nested or complex data structures, such as lists and vectors. -The module is loaded by simply saying. +The module is loaded by entering the following: @lisp (use-modules (ice-9 pretty-print)) @@ -60,6 +60,65 @@ Print within the given @var{columns}. The default is 79. @end deffn +@cindex truncated printing +Also exported by the @code{(ice-9 pretty-print)} module is +@code{truncated-print}, a procedure to print Scheme datums, truncating +the output to a certain number of characters. This is useful when you +need to present an arbitrary datum to the user, but you only have one +line in which to do so. + +@lisp +(define exp '(a b #(c d e) f . g)) +(truncated-print exp #:width 10) (newline) +@print{} (a b . #) +(truncated-print exp #:width 15) (newline) +@print{} (a b # f . g) +(truncated-print exp #:width 18) (newline) +@print{} (a b #(c ...) . #) +(truncated-print exp #:width 20) (newline) +@print{} (a b #(c d e) f . g) +(truncated-print "The quick brown fox" #:width 10) (newline) +@print{} "The quick brown..." +(truncated-print (current-module) #:width 20) (newline) +@print{} #<directory (gui...> +@end lisp + +@code{truncated-print} will not output a trailing newline. If an +expression does not fit in the given width, it will be truncated -- +possibly ellipsized, or in the worst case, displayed as @nicode{#}. + +@deffn {Scheme Procedure} truncated-print obj [port] [keyword-options] +Print @var{obj}, truncating the output, if necessary, to make it fit +into @var{width} characters. By default, @var{x} will be printed using +@code{write}, though that behavior can be overriden via the +@var{display?} keyword argument. + +The default behaviour is to print depth-first, meaning that the entire +remaining width will be available to each sub-expressoin of @var{x} -- +e.g., if @var{x} is a vector, each member of @var{x}. One can attempt to +``ration'' the available width, trying to allocate it equally to each +sub-expression, via the @var{breadth-first?} keyword argument. + +The further @var{keyword-options} are keywords and parameters as +follows, + +@table @asis +@item @nicode{#:display?} @var{flag} +If @var{flag} is true then print using @code{display}. The default is +@code{#f} which means use @code{write} style. (@pxref{Writing}) + +@item @nicode{#:width} @var{columns} +Print within the given @var{columns}. The default is 79. + +@item @nicode{#:breadth-first?} @var{flag} +If @var{flag} is true, then allocate the available width breadth-first +among elements of a compound data structure (list, vector, pair, +etc.). The default is @code{#f} which means that any element is +allowed to consume all of the available width. +@end table +@end deffn + + @page @node Formatted Output @section Formatted Output @@ -577,9 +636,17 @@ to help. When using @code{gettext} to translate messages (@pxref{Internationalization}). @item @nicode{~y} -Pretty print. No parameters. +Structured printing. Parameters: @var{width}. + +@nicode{~y} outputs an argument using @code{pretty-print} +(@pxref{Pretty Printing}). The result will be formatted to fit within +@var{width} columns (79 by default), consuming multiple lines if +necessary. -Output an argument with @code{pretty-print} (@pxref{Pretty Printing}). +@nicode{~@@y} outputs an argument using @code{truncated-print} +(@pxref{Pretty Printing}). The resulting code will be formatted to fit +within @var{width} columns (79 by default), on a single line. The +output will be truncated if necessary. @item @nicode{~?} @itemx @nicode{~k} |