; Improve documentation of character classes in regexps

* doc/lispref/searching.texi (Char Classes): Add notes about the
dependence of character classes on case and syntax tables specific
to buffers and modes.  (Bug#58992)

1 files changed, 18 insertions, 8 deletions

diff --git a/doc/lispref/searching.texi b/doc/lispref/searching.texi
index fe4de0abbb2..3365c0c9042 100644
--- a/doc/lispref/searching.texi
+++ b/doc/lispref/searching.texi
@@ -617,7 +617,7 @@ This matches any character whose code is in the range 0--31.
 This matches @samp{0} through @samp{9}.  Thus, @samp{[-+[:digit:]]}
 matches any digit, as well as @samp{+} and @samp{-}.
 @item [:graph:]
-This matches graphic characters---everything except whitespace,
+This matches graphic characters---everything except spaces,
 @acronym{ASCII} and non-@acronym{ASCII} control characters,
 surrogates, and codepoints unassigned by Unicode, as indicated by the
 Unicode @samp{general-category} property (@pxref{Character
@@ -625,29 +625,39 @@ Properties}).
 @item [:lower:]
 This matches any lower-case letter, as determined by the current case
 table (@pxref{Case Tables}).  If @code{case-fold-search} is
-non-@code{nil}, this also matches any upper-case letter.
+non-@code{nil}, this also matches any upper-case letter.  Note that a
+buffer can have its own local case table different from the default
+one.
 @item [:multibyte:]
 This matches any multibyte character (@pxref{Text Representations}).
 @item [:nonascii:]
 This matches any non-@acronym{ASCII} character.
 @item [:print:]
-This matches any printing character---either whitespace, or a graphic
-character matched by @samp{[:graph:]}.
+This matches any printing character---either spaces or graphic
+characters matched by @samp{[:graph:]}.
 @item [:punct:]
 This matches any punctuation character.  (At present, for multibyte
-characters, it matches anything that has non-word syntax.)
+characters, it matches anything that has non-word syntax, and thus its
+exact definition can vary from one major mode to another, since the
+syntax of a character depends on the major mode.)
 @item [:space:]
 This matches any character that has whitespace syntax
-(@pxref{Syntax Class Table}).
+(@pxref{Syntax Class Table}).  Note that the syntax of a character,
+and thus which characters are considered ``whitespace'',
+depends on the major mode.
 @item [:unibyte:]
 This matches any unibyte character (@pxref{Text Representations}).
 @item [:upper:]
 This matches any upper-case letter, as determined by the current case
 table (@pxref{Case Tables}).  If @code{case-fold-search} is
-non-@code{nil}, this also matches any lower-case letter.
+non-@code{nil}, this also matches any lower-case letter.  Note that a
+buffer can have its own local case table different from the default
+one.
 @item [:word:]
 This matches any character that has word syntax (@pxref{Syntax Class
-Table}).
+Table}).  Note that the syntax of a character, and thus which
+characters are considered ``word-constituent'', depends on the major
+mode.
 @item [:xdigit:]
 This matches the hexadecimal digits: @samp{0} through @samp{9}, @samp{a}
 through @samp{f} and @samp{A} through @samp{F}.