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; Minor fixes of recently-installed regexp documentation changes

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* doc/emacs/search.texi (Regexps):
* doc/lispref/searching.texi (Regexp Special): Keep the old
terminology as "a.k.a.".
(Char Classes, POSIX Regexps, POSIX Regexps): Add cross-references
to where "bracket expression" is defined.  (Bug#64128)
This commit is contained in:
Eli Zaretskii 2023-06-22 08:32:16 +03:00
parent 72f1c12e58
commit 4848bdf98b
2 changed files with 36 additions and 32 deletions
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3
doc/emacs/search.texi
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@ -1037,7 +1037,8 @@ starting at the first @samp{a}, it does.
@cindex set of alternative characters, in regular expressions
@cindex character set, in regular expressions
@item @kbd{[ @dots{} ]}
is a @dfn{bracket expression}, which matches one of a set of characters.
is a @dfn{bracket expression} (a.k.a.@: @dfn{set of alternative
characters}), which matches one of a set of characters.
In the simplest case, the characters between the two brackets are what
this set can match. Thus, @samp{[ad]} matches either one @samp{a} or

65
doc/lispref/searching.texi
View file

@ -375,11 +375,13 @@ permits the whole expression to match is @samp{d}.)
@item @samp{[ @dots{} ]}
@cindex bracket expression (in regexp)
@cindex character alternative (in regexp)
@cindex @samp{[} in regexp
@cindex @samp{]} in regexp
is a @dfn{bracket expression}, which begins with @samp{[} and is
terminated by @samp{]}. In the simplest case, the characters between
the two brackets are what this bracket expression can match.
is a @dfn{bracket expression} (a.k.a.@: @dfn{character alternative}),
which begins with @samp{[} and is terminated by @samp{]}. In the
simplest case, the characters between the two brackets are what this
bracket expression can match.
Thus, @samp{[ad]} matches either one @samp{a} or one @samp{d}, and
@samp{[ad]*} matches any string composed of just @samp{a}s and @samp{d}s
@ -478,10 +480,10 @@ style; and although @samp{[*--]} is valid, @samp{[*+,-]} is clearer.
@item @samp{[^ @dots{} ]}
@cindex @samp{^} in regexp
@samp{[^} begins a @dfn{complemented bracket expression}. This
matches any character except the ones specified. Thus,
@samp{[^a-z0-9A-Z]} matches all characters @emph{except} ASCII letters and
digits.
@samp{[^} begins a @dfn{complemented bracket expression}, or
@dfn{complemented character alternative}. This matches any character
except the ones specified. Thus, @samp{[^a-z0-9A-Z]} matches all
characters @emph{except} ASCII letters and digits.
@samp{^} is not special in a bracket expression unless it is the first
character. The character following the @samp{^} is treated as if it
@ -588,13 +590,13 @@ an unquoted @samp{[} is special again and a @samp{]} not.
@cindex alpha character class, regexp
@cindex xdigit character class, regexp
Below is a table of the classes you can use in a bracket
expression, and what they mean. Note that the @samp{[} and @samp{]}
characters that enclose the class name are part of the name, so a
regular expression using these classes needs one more pair of
brackets. For example, a regular expression matching a sequence of
one or more letters and digits would be @samp{[[:alnum:]]+}, not
@samp{[:alnum:]+}.
Below is a table of the classes you can use in a bracket expression
(@pxref{Regexp Special, bracket expression}), and what they mean.
Note that the @samp{[} and @samp{]} characters that enclose the class
name are part of the name, so a regular expression using these classes
needs one more pair of brackets. For example, a regular expression
matching a sequence of one or more letters and digits would be
@samp{[[:alnum:]]+}, not @samp{[:alnum:]+}.
@table @samp
@item [:ascii:]
@ -2993,6 +2995,24 @@ POSIX does not define how other BRE escapes behave;
for example, GNU @command{grep} treats @samp{\|} like Emacs does,
but does not support all the Emacs escapes.
@item
In POSIX BREs, it is an implementation option whether @samp{^} is special
after @samp{\(}; GNU @command{grep} treats it like Emacs does.
In POSIX EREs, @samp{^} is always special outside of bracket expressions,
which means the ERE @samp{x^} never matches.
In Emacs regular expressions, @samp{^} is special only at the
beginning of the regular expression, or after @samp{\(}, @samp{\(?:}
or @samp{\|}.
@item
In POSIX BREs, it is an implementation option whether @samp{$} is
special before @samp{\)}; GNU @command{grep} treats it like Emacs
does. In POSIX EREs, @samp{$} is always special outside of bracket
expressions (@pxref{Regexp Special, bracket expressions}), which means
the ERE @samp{$x} never matches. In Emacs regular expressions,
@samp{$} is special only at the end of the regular expression, or
before @samp{\)} or @samp{\|}.
@item
In POSIX EREs @samp{@{}, @samp{(} and @samp{|} are special,
and @samp{)} is special when matched with a preceding @samp{(}.
@ -3005,23 +3025,6 @@ POSIX does not define how other ERE escapes behave;
for example, GNU @samp{grep -E} treats @samp{\1} like Emacs does,
but does not support all the Emacs escapes.
@item
In POSIX BREs, it is an implementation option whether @samp{^} is special
after @samp{\(}; GNU @command{grep} treats it like Emacs does.
In POSIX EREs, @samp{^} is always special outside of bracket expressions,
which means the ERE @samp{x^} never matches.
In Emacs regular expressions, @samp{^} is special only at the
beginning of the regular expression, or after @samp{\(}, @samp{\(?:}
or @samp{\|}.
@item
In POSIX BREs, it is an implementation option whether @samp{$} is special
before @samp{\)}; GNU @command{grep} treats it like Emacs does.
In POSIX EREs, @samp{$} is always special outside of bracket expressions,
which means the ERE @samp{$x} never matches.
In Emacs regular expressions, @samp{$} is special only at the
end of the regular expression, or before @samp{\)} or @samp{\|}.
@item
In POSIX BREs and EREs, undefined results are produced by repetition
operators at the start of a regular expression or subexpression