@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1990, 1991, 1992, 1993, 1994 Free Software Foundation, Inc.
+@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2002, 2003,
+@c 2004, 2005, 2006 Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@setfilename ../info/searching
-@node Searching and Matching, Syntax Tables, Text, Top
+@node Searching and Matching, Syntax Tables, Non-ASCII Characters, Top
@chapter Searching and Matching
@cindex searching
@menu
* String Search:: Search for an exact match.
+* Searching and Case:: Case-independent or case-significant searching.
* Regular Expressions:: Describing classes of strings.
* Regexp Search:: Searching for a match for a regexp.
-* Search and Replace:: Internals of @code{query-replace}.
-* Match Data:: Finding out which part of the text matched
- various parts of a regexp, after regexp search.
-* Searching and Case:: Case-independent or case-significant searching.
+* POSIX Regexps:: Searching POSIX-style for the longest match.
+* Match Data:: Finding out which part of the text matched,
+ after a string or regexp search.
+* Search and Replace:: Commands that loop, searching and replacing.
* Standard Regexps:: Useful regexps for finding sentences, pages,...
@end menu
The @samp{skip-chars@dots{}} functions also perform a kind of searching.
-@xref{Skipping Characters}.
+@xref{Skipping Characters}. To search for changes in character
+properties, see @ref{Property Search}.
@node String Search
@section Searching for Strings
These are the primitive functions for searching through the text in a
buffer. They are meant for use in programs, but you may call them
-interactively. If you do so, they prompt for the search string;
-@var{limit} and @var{noerror} are set to @code{nil}, and @var{repeat}
-is set to 1.
+interactively. If you do so, they prompt for the search string; the
+arguments @var{limit} and @var{noerror} are @code{nil}, and @var{repeat}
+is 1.
+
+ These search functions convert the search string to multibyte if the
+buffer is multibyte; they convert the search string to unibyte if the
+buffer is unibyte. @xref{Text Representations}.
@deffn Command search-forward string &optional limit noerror repeat
- This function searches forward from point for an exact match for
+This function searches forward from point for an exact match for
@var{string}. If successful, it sets point to the end of the occurrence
found, and returns the new value of point. If no match is found, the
value and side effects depend on @var{noerror} (see below).
@c Emacs 19 feature
- In the following example, point is initially at the beginning of the
+In the following example, point is initially at the beginning of the
line. Then @code{(search-forward "fox")} moves point after the last
letter of @samp{fox}:
@end group
@end example
- The argument @var{limit} specifies the upper bound to the search. (It
+The argument @var{limit} specifies the upper bound to the search. (It
must be a position in the current buffer.) No match extending after
that position is accepted. If @var{limit} is omitted or @code{nil}, it
defaults to the end of the accessible portion of the buffer.
@kindex search-failed
- What happens when the search fails depends on the value of
+What happens when the search fails depends on the value of
@var{noerror}. If @var{noerror} is @code{nil}, a @code{search-failed}
error is signaled. If @var{noerror} is @code{t}, @code{search-forward}
returns @code{nil} and does nothing. If @var{noerror} is neither
@code{nil} nor @code{t}, then @code{search-forward} moves point to the
-upper bound and returns @code{nil}. (It would be more consistent now
-to return the new position of point in that case, but some programs
-may depend on a value of @code{nil}.)
+upper bound and returns @code{nil}. (It would be more consistent now to
+return the new position of point in that case, but some existing
+programs may depend on a value of @code{nil}.)
- If @var{repeat} is non-@code{nil}, then the search is repeated that
-many times. Point is positioned at the end of the last match.
+The argument @var{noerror} only affects valid searches which fail to
+find a match. Invalid arguments cause errors regardless of
+@var{noerror}.
+
+If @var{repeat} is supplied (it must be a positive number), then the
+search is repeated that many times (each time starting at the end of the
+previous time's match). If these successive searches succeed, the
+function succeeds, moving point and returning its new value. Otherwise
+the search fails, with results depending on the value of
+@var{noerror}, as described above.
@end deffn
@deffn Command search-backward string &optional limit noerror repeat
@end group
@end example
-If @var{limit} is non-@code{nil} (it must be a position in the current
-buffer), then it is the upper bound to the search. The match found must
-not extend after that position.
+If @var{limit} is non-@code{nil}, it must be a position in the current
+buffer; it specifies the upper bound to the search. The match found
+must not extend after that position.
If @var{noerror} is @code{nil}, then @code{word-search-forward} signals
an error if the search fails. If @var{noerror} is @code{t}, then it
returns @code{nil} instead of signaling an error. If @var{noerror} is
neither @code{nil} nor @code{t}, it moves point to @var{limit} (or the
-end of the buffer) and returns @code{nil}.
+end of the accessible portion of the buffer) and returns @code{nil}.
If @var{repeat} is non-@code{nil}, then the search is repeated that many
times. Point is positioned at the end of the last match.
beginning of the match.
@end deffn
+@node Searching and Case
+@section Searching and Case
+@cindex searching and case
+
+ By default, searches in Emacs ignore the case of the text they are
+searching through; if you specify searching for @samp{FOO}, then
+@samp{Foo} or @samp{foo} is also considered a match. This applies to
+regular expressions, too; thus, @samp{[aB]} would match @samp{a} or
+@samp{A} or @samp{b} or @samp{B}.
+
+ If you do not want this feature, set the variable
+@code{case-fold-search} to @code{nil}. Then all letters must match
+exactly, including case. This is a buffer-local variable; altering the
+variable affects only the current buffer. (@xref{Intro to
+Buffer-Local}.) Alternatively, you may change the value of
+@code{default-case-fold-search}, which is the default value of
+@code{case-fold-search} for buffers that do not override it.
+
+ Note that the user-level incremental search feature handles case
+distinctions differently. When given a lower case letter, it looks for
+a match of either case, but when given an upper case letter, it looks
+for an upper case letter only. But this has nothing to do with the
+searching functions used in Lisp code.
+
+@defopt case-replace
+This variable determines whether the higher level replacement
+functions should preserve case. If the variable is @code{nil}, that
+means to use the replacement text verbatim. A non-@code{nil} value
+means to convert the case of the replacement text according to the
+text being replaced.
+
+This variable is used by passing it as an argument to the function
+@code{replace-match}. @xref{Replacing Match}.
+@end defopt
+
+@defopt case-fold-search
+This buffer-local variable determines whether searches should ignore
+case. If the variable is @code{nil} they do not ignore case; otherwise
+they do ignore case.
+@end defopt
+
+@defvar default-case-fold-search
+The value of this variable is the default value for
+@code{case-fold-search} in buffers that do not override it. This is the
+same as @code{(default-value 'case-fold-search)}.
+@end defvar
+
@node Regular Expressions
@section Regular Expressions
@cindex regular expression
a regexp is a very powerful operation. This section explains how to write
regexps; the following section says how to search for them.
+@findex re-builder
+@cindex authoring regular expressions
+ For convenient interactive development of regular expressions, you
+can use the @kbd{M-x re-builder} command. It provides a convenient
+interface for creating regular expressions, by giving immediate visual
+feedback in a separate buffer. As you edit the regexp, all its
+matches in the target buffer are highlighted. Each parenthesized
+sub-expression of the regexp is shown in a distinct face, which makes
+it easier to verify even very complex regexps.
+
@menu
* Syntax of Regexps:: Rules for writing regular expressions.
* Regexp Example:: Illustrates regular expression syntax.
+* Regexp Functions:: Functions for operating on regular expressions.
@end menu
@node Syntax of Regexps
@subsection Syntax of Regular Expressions
- Regular expressions have a syntax in which a few characters are special
-constructs and the rest are @dfn{ordinary}. An ordinary character is a
-simple regular expression which matches that character and nothing else.
-The special characters are @samp{$}, @samp{^}, @samp{.}, @samp{*},
-@samp{+}, @samp{?}, @samp{[}, @samp{]} and @samp{\}; no new special
-characters will be defined in the future. Any other character appearing
-in a regular expression is ordinary, unless a @samp{\} precedes it.
-
-For example, @samp{f} is not a special character, so it is ordinary, and
+ Regular expressions have a syntax in which a few characters are
+special constructs and the rest are @dfn{ordinary}. An ordinary
+character is a simple regular expression that matches that character
+and nothing else. The special characters are @samp{.}, @samp{*},
+@samp{+}, @samp{?}, @samp{[}, @samp{^}, @samp{$}, and @samp{\}; no new
+special characters will be defined in the future. The character
+@samp{]} is special if it ends a character alternative (see later).
+The character @samp{-} is special inside a character alternative. A
+@samp{[:} and balancing @samp{:]} enclose a character class inside a
+character alternative. Any other character appearing in a regular
+expression is ordinary, unless a @samp{\} precedes it.
+
+ For example, @samp{f} is not a special character, so it is ordinary, and
therefore @samp{f} is a regular expression that matches the string
@samp{f} and no other string. (It does @emph{not} match the string
-@samp{ff}.) Likewise, @samp{o} is a regular expression that matches
-only @samp{o}.@refill
+@samp{fg}, but it does match a @emph{part} of that string.) Likewise,
+@samp{o} is a regular expression that matches only @samp{o}.@refill
-Any two regular expressions @var{a} and @var{b} can be concatenated. The
-result is a regular expression which matches a string if @var{a} matches
+ Any two regular expressions @var{a} and @var{b} can be concatenated. The
+result is a regular expression that matches a string if @var{a} matches
some amount of the beginning of that string and @var{b} matches the rest of
the string.@refill
-As a simple example, we can concatenate the regular expressions @samp{f}
+ As a simple example, we can concatenate the regular expressions @samp{f}
and @samp{o} to get the regular expression @samp{fo}, which matches only
the string @samp{fo}. Still trivial. To do something more powerful, you
-need to use one of the special characters. Here is a list of them:
+need to use one of the special regular expression constructs.
+
+@menu
+* Regexp Special:: Special characters in regular expressions.
+* Char Classes:: Character classes used in regular expressions.
+* Regexp Backslash:: Backslash-sequences in regular expressions.
+@end menu
+
+@node Regexp Special
+@subsubsection Special Characters in Regular Expressions
-@need 1200
-@table @kbd
-@item .@: @r{(Period)}
+ Here is a list of the characters that are special in a regular
+expression.
+
+@need 800
+@table @asis
+@item @samp{.}@: @r{(Period)}
@cindex @samp{.} in regexp
is a special character that matches any single character except a newline.
Using concatenation, we can make regular expressions like @samp{a.b}, which
matches any three-character string that begins with @samp{a} and ends with
@samp{b}.@refill
-@item *
+@item @samp{*}
@cindex @samp{*} in regexp
-is not a construct by itself; it is a suffix operator that means to
-repeat the preceding regular expression as many times as possible. In
-@samp{fo*}, the @samp{*} applies to the @samp{o}, so @samp{fo*} matches
-one @samp{f} followed by any number of @samp{o}s. The case of zero
-@samp{o}s is allowed: @samp{fo*} does match @samp{f}.@refill
+is not a construct by itself; it is a postfix operator that means to
+match the preceding regular expression repetitively as many times as
+possible. Thus, @samp{o*} matches any number of @samp{o}s (including no
+@samp{o}s).
@samp{*} always applies to the @emph{smallest} possible preceding
-expression. Thus, @samp{fo*} has a repeating @samp{o}, not a
-repeating @samp{fo}.@refill
-
-The matcher processes a @samp{*} construct by matching, immediately,
-as many repetitions as can be found. Then it continues with the rest
-of the pattern. If that fails, backtracking occurs, discarding some
-of the matches of the @samp{*}-modified construct in case that makes
-it possible to match the rest of the pattern. For example, in matching
-@samp{ca*ar} against the string @samp{caaar}, the @samp{a*} first
-tries to match all three @samp{a}s; but the rest of the pattern is
+expression. Thus, @samp{fo*} has a repeating @samp{o}, not a repeating
+@samp{fo}. It matches @samp{f}, @samp{fo}, @samp{foo}, and so on.
+
+The matcher processes a @samp{*} construct by matching, immediately, as
+many repetitions as can be found. Then it continues with the rest of
+the pattern. If that fails, backtracking occurs, discarding some of the
+matches of the @samp{*}-modified construct in the hope that that will
+make it possible to match the rest of the pattern. For example, in
+matching @samp{ca*ar} against the string @samp{caaar}, the @samp{a*}
+first tries to match all three @samp{a}s; but the rest of the pattern is
@samp{ar} and there is only @samp{r} left to match, so this try fails.
-The next alternative is for @samp{a*} to match only two @samp{a}s.
-With this choice, the rest of the regexp matches successfully.@refill
-
-@item +
+The next alternative is for @samp{a*} to match only two @samp{a}s. With
+this choice, the rest of the regexp matches successfully.
+
+@strong{Warning:} Nested repetition operators take a long time,
+or even forever, if they
+lead to ambiguous matching. For example, trying to match the regular
+expression @samp{\(x+y*\)*a} against the string
+@samp{xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxz} could take hours before it
+ultimately fails. Emacs must try each way of grouping the 35
+@samp{x}s before concluding that none of them can work. Even worse,
+@samp{\(x*\)*} can match the null string in infinitely many ways, so
+it causes an infinite loop. To avoid these problems, check nested
+repetitions carefully, to make sure that they do not cause combinatorial
+explosions in backtracking.
+
+@item @samp{+}
@cindex @samp{+} in regexp
-is a suffix operator similar to @samp{*} except that the preceding
-expression must match at least once. So, for example, @samp{ca+r}
+is a postfix operator, similar to @samp{*} except that it must match
+the preceding expression at least once. So, for example, @samp{ca+r}
matches the strings @samp{car} and @samp{caaaar} but not the string
@samp{cr}, whereas @samp{ca*r} matches all three strings.
-@item ?
+@item @samp{?}
@cindex @samp{?} in regexp
-is a suffix operator similar to @samp{*} except that the preceding
-expression can match either once or not at all. For example,
-@samp{ca?r} matches @samp{car} or @samp{cr}, but does not match anyhing
-else.
-
-@item [ @dots{} ]
-@cindex character set (in regexp)
+is a postfix operator, similar to @samp{*} except that it must match the
+preceding expression either once or not at all. For example,
+@samp{ca?r} matches @samp{car} or @samp{cr}; nothing else.
+
+@item @samp{*?}, @samp{+?}, @samp{??}
+These are ``non-greedy'' variants of the operators @samp{*}, @samp{+}
+and @samp{?}. Where those operators match the largest possible
+substring (consistent with matching the entire containing expression),
+the non-greedy variants match the smallest possible substring
+(consistent with matching the entire containing expression).
+
+For example, the regular expression @samp{c[ad]*a} when applied to the
+string @samp{cdaaada} matches the whole string; but the regular
+expression @samp{c[ad]*?a}, applied to that same string, matches just
+@samp{cda}. (The smallest possible match here for @samp{[ad]*?} that
+permits the whole expression to match is @samp{d}.)
+
+@item @samp{[ @dots{} ]}
+@cindex character alternative (in regexp)
@cindex @samp{[} in regexp
@cindex @samp{]} in regexp
-@samp{[} begins a @dfn{character set}, which is terminated by a
-@samp{]}. In the simplest case, the characters between the two brackets
-form the set. 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 (including the empty string), from which it follows that
-@samp{c[ad]*r} matches @samp{cr}, @samp{car}, @samp{cdr},
-@samp{caddaar}, etc.@refill
-
-The usual regular expression special characters are not special inside a
-character set. A completely different set of special characters exists
-inside character sets: @samp{]}, @samp{-} and @samp{^}.@refill
-
-@samp{-} is used for ranges of characters. To write a range, write two
-characters with a @samp{-} between them. Thus, @samp{[a-z]} matches any
-lower case letter. Ranges may be intermixed freely with individual
-characters, as in @samp{[a-z$%.]}, which matches any lower case letter
-or @samp{$}, @samp{%} or a period.@refill
-
-To include a @samp{]} in a character set, make it the first character.
-For example, @samp{[]a]} matches @samp{]} or @samp{a}. To include a
-@samp{-}, write @samp{-} as the first character in the set, or put
-immediately after a range. (You can replace one individual character
-@var{c} with the range @samp{@var{c}-@var{c}} to make a place to put the
-@samp{-}). There is no way to write a set containing just @samp{-} and
-@samp{]}.
-
-To include @samp{^} in a set, put it anywhere but at the beginning of
-the set.
-
-@item [^ @dots{} ]
+is 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 character alternative 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
+(including the empty string), from which it follows that @samp{c[ad]*r}
+matches @samp{cr}, @samp{car}, @samp{cdr}, @samp{caddaar}, etc.
+
+You can also include character ranges in a character alternative, by
+writing the starting and ending characters with a @samp{-} between them.
+Thus, @samp{[a-z]} matches any lower-case @acronym{ASCII} letter.
+Ranges may be intermixed freely with individual characters, as in
+@samp{[a-z$%.]}, which matches any lower case @acronym{ASCII} letter
+or @samp{$}, @samp{%} or period.
+
+Note that the usual regexp special characters are not special inside a
+character alternative. A completely different set of characters is
+special inside character alternatives: @samp{]}, @samp{-} and @samp{^}.
+
+To include a @samp{]} in a character alternative, you must make it the
+first character. For example, @samp{[]a]} matches @samp{]} or @samp{a}.
+To include a @samp{-}, write @samp{-} as the first or last character of
+the character alternative, or put it after a range. Thus, @samp{[]-]}
+matches both @samp{]} and @samp{-}.
+
+To include @samp{^} in a character alternative, put it anywhere but at
+the beginning.
+
+The beginning and end of a range of multibyte characters must be in
+the same character set (@pxref{Character Sets}). Thus,
+@code{"[\x8e0-\x97c]"} is invalid because character 0x8e0 (@samp{a}
+with grave accent) is in the Emacs character set for Latin-1 but the
+character 0x97c (@samp{u} with diaeresis) is in the Emacs character
+set for Latin-2. (We use Lisp string syntax to write that example,
+and a few others in the next few paragraphs, in order to include hex
+escape sequences in them.)
+
+If a range starts with a unibyte character @var{c} and ends with a
+multibyte character @var{c2}, the range is divided into two parts: one
+is @samp{@var{c}..?\377}, the other is @samp{@var{c1}..@var{c2}}, where
+@var{c1} is the first character of the charset to which @var{c2}
+belongs.
+
+You cannot always match all non-@acronym{ASCII} characters with the regular
+expression @code{"[\200-\377]"}. This works when searching a unibyte
+buffer or string (@pxref{Text Representations}), but not in a multibyte
+buffer or string, because many non-@acronym{ASCII} characters have codes
+above octal 0377. However, the regular expression @code{"[^\000-\177]"}
+does match all non-@acronym{ASCII} characters (see below regarding @samp{^}),
+in both multibyte and unibyte representations, because only the
+@acronym{ASCII} characters are excluded.
+
+A character alternative can also specify named
+character classes (@pxref{Char Classes}). This is a POSIX feature whose
+syntax is @samp{[:@var{class}:]}. Using a character class is equivalent
+to mentioning each of the characters in that class; but the latter is
+not feasible in practice, since some classes include thousands of
+different characters.
+
+@item @samp{[^ @dots{} ]}
@cindex @samp{^} in regexp
-@samp{[^} begins a @dfn{complement character set}, which matches any
-character except the ones specified. Thus, @samp{[^a-z0-9A-Z]}
-matches all characters @emph{except} letters and digits.@refill
+@samp{[^} begins a @dfn{complemented character alternative}. This
+matches any character except the ones specified. Thus,
+@samp{[^a-z0-9A-Z]} matches all characters @emph{except} letters and
+digits.
-@samp{^} is not special in a character set unless it is the first
+@samp{^} is not special in a character alternative unless it is the first
character. The character following the @samp{^} is treated as if it
-were first (thus, @samp{-} and @samp{]} are not special there).
+were first (in other words, @samp{-} and @samp{]} are not special there).
-Note that a complement character set can match a newline, unless
-newline is mentioned as one of the characters not to match.
+A complemented character alternative can match a newline, unless newline is
+mentioned as one of the characters not to match. This is in contrast to
+the handling of regexps in programs such as @code{grep}.
-@item ^
-@cindex @samp{^} in regexp
+@item @samp{^}
@cindex beginning of line in regexp
-is a special character that matches the empty string, but only at
-the beginning of a line in the text being matched. Otherwise it fails
-to match anything. Thus, @samp{^foo} matches a @samp{foo} which occurs
-at the beginning of a line.
+When matching a buffer, @samp{^} matches the empty string, but only at the
+beginning of a line in the text being matched (or the beginning of the
+accessible portion of the buffer). Otherwise it fails to match
+anything. Thus, @samp{^foo} matches a @samp{foo} that occurs at the
+beginning of a line.
+
+When matching a string instead of a buffer, @samp{^} matches at the
+beginning of the string or after a newline character.
-When matching a string, @samp{^} matches at the beginning of the string
-or after a newline character @samp{\n}.
+For historical compatibility reasons, @samp{^} can be used only at the
+beginning of the regular expression, or after @samp{\(} or @samp{\|}.
-@item $
+@item @samp{$}
@cindex @samp{$} in regexp
-is similar to @samp{^} but matches only at the end of a line. Thus,
-@samp{x+$} matches a string of one @samp{x} or more at the end of a line.
+@cindex end of line in regexp
+is similar to @samp{^} but matches only at the end of a line (or the
+end of the accessible portion of the buffer). Thus, @samp{x+$}
+matches a string of one @samp{x} or more at the end of a line.
-When matching a string, @samp{$} matches at the end of the string
-or before a newline character @samp{\n}.
+When matching a string instead of a buffer, @samp{$} matches at the end
+of the string or before a newline character.
-@item \
+For historical compatibility reasons, @samp{$} can be used only at the
+end of the regular expression, or before @samp{\)} or @samp{\|}.
+
+@item @samp{\}
@cindex @samp{\} in regexp
has two functions: it quotes the special characters (including
@samp{\}), and it introduces additional special constructs.
Because @samp{\} quotes special characters, @samp{\$} is a regular
-expression which matches only @samp{$}, and @samp{\[} is a regular
-expression which matches only @samp{[}, and so on.
+expression that matches only @samp{$}, and @samp{\[} is a regular
+expression that matches only @samp{[}, and so on.
Note that @samp{\} also has special meaning in the read syntax of Lisp
strings (@pxref{String Type}), and must be quoted with @samp{\}. For
@samp{\} is @code{"\\\\"}.@refill
@end table
-@strong{Please note:} for historical compatibility, special characters
+@strong{Please note:} For historical compatibility, special characters
are treated as ordinary ones if they are in contexts where their special
meanings make no sense. For example, @samp{*foo} treats @samp{*} as
ordinary since there is no preceding expression on which the @samp{*}
-can act. It is poor practice to depend on this behavior; better to
-quote the special character anyway, regardless of where it
-appears.@refill
+can act. It is poor practice to depend on this behavior; quote the
+special character anyway, regardless of where it appears.@refill
+
+As a @samp{\} is not special inside a character alternative, it can
+never remove the special meaning of @samp{-} or @samp{]}. So you
+should not quote these characters when they have no special meaning
+either. This would not clarify anything, since backslashes can
+legitimately precede these characters where they @emph{have} special
+meaning, as in @samp{[^\]} (@code{"[^\\]"} for Lisp string syntax),
+which matches any single character except a backslash.
+
+In practice, most @samp{]} that occur in regular expressions close a
+character alternative and hence are special. However, occasionally a
+regular expression may try to match a complex pattern of literal
+@samp{[} and @samp{]}. In such situations, it sometimes may be
+necessary to carefully parse the regexp from the start to determine
+which square brackets enclose a character alternative. For example,
+@samp{[^][]]} consists of the complemented character alternative
+@samp{[^][]} (which matches any single character that is not a square
+bracket), followed by a literal @samp{]}.
+
+The exact rules are that at the beginning of a regexp, @samp{[} is
+special and @samp{]} not. This lasts until the first unquoted
+@samp{[}, after which we are in a character alternative; @samp{[} is
+no longer special (except when it starts a character class) but @samp{]}
+is special, unless it immediately follows the special @samp{[} or that
+@samp{[} followed by a @samp{^}. This lasts until the next special
+@samp{]} that does not end a character class. This ends the character
+alternative and restores the ordinary syntax of regular expressions;
+an unquoted @samp{[} is special again and a @samp{]} not.
+
+@node Char Classes
+@subsubsection Character Classes
+@cindex character classes in regexp
+
+ Here is a table of the classes you can use in a character alternative,
+and what they mean:
+
+@table @samp
+@item [:ascii:]
+This matches any @acronym{ASCII} character (codes 0--127).
+@item [:alnum:]
+This matches any letter or digit. (At present, for multibyte
+characters, it matches anything that has word syntax.)
+@item [:alpha:]
+This matches any letter. (At present, for multibyte characters, it
+matches anything that has word syntax.)
+@item [:blank:]
+This matches space and tab only.
+@item [:cntrl:]
+This matches any @acronym{ASCII} control character.
+@item [:digit:]
+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 @acronym{ASCII} control
+characters, space, and the delete character.
+@item [:lower:]
+This matches any lower-case letter, as determined by
+the current case table (@pxref{Case Tables}).
+@item [:multibyte:]
+This matches any multibyte character (@pxref{Text Representations}).
+@item [:nonascii:]
+This matches any non-@acronym{ASCII} character.
+@item [:print:]
+This matches printing characters---everything except @acronym{ASCII} control
+characters and the delete character.
+@item [:punct:]
+This matches any punctuation character. (At present, for multibyte
+characters, it matches anything that has non-word syntax.)
+@item [:space:]
+This matches any character that has whitespace syntax
+(@pxref{Syntax Class Table}).
+@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}).
+@item [:word:]
+This matches any character that has word syntax (@pxref{Syntax Class
+Table}).
+@item [:xdigit:]
+This matches the hexadecimal digits: @samp{0} through @samp{9}, @samp{a}
+through @samp{f} and @samp{A} through @samp{F}.
+@end table
+
+@node Regexp Backslash
+@subsubsection Backslash Constructs in Regular Expressions
-For the most part, @samp{\} followed by any character matches only
-that character. However, there are several exceptions: characters
-which, when preceded by @samp{\}, are special constructs. Such
-characters are always ordinary when encountered on their own. Here
-is a table of @samp{\} constructs:
+ For the most part, @samp{\} followed by any character matches only
+that character. However, there are several exceptions: certain
+two-character sequences starting with @samp{\} that have special
+meanings. (The character after the @samp{\} in such a sequence is
+always ordinary when used on its own.) Here is a table of the special
+@samp{\} constructs.
-@table @kbd
+@table @samp
@item \|
@cindex @samp{|} in regexp
@cindex regexp alternative
surrounding @samp{\( @dots{} \)} grouping can limit the grouping power of
@samp{\|}.@refill
-Full backtracking capability exists to handle multiple uses of @samp{\|}.
+If you need full backtracking capability to handle multiple uses of
+@samp{\|}, use the POSIX regular expression functions (@pxref{POSIX
+Regexps}).
+
+@item \@{@var{m}\@}
+is a postfix operator that repeats the previous pattern exactly @var{m}
+times. Thus, @samp{x\@{5\@}} matches the string @samp{xxxxx}
+and nothing else. @samp{c[ad]\@{3\@}r} matches string such as
+@samp{caaar}, @samp{cdddr}, @samp{cadar}, and so on.
+
+@item \@{@var{m},@var{n}\@}
+is a more general postfix operator that specifies repetition with a
+minimum of @var{m} repeats and a maximum of @var{n} repeats. If @var{m}
+is omitted, the minimum is 0; if @var{n} is omitted, there is no
+maximum.
+
+For example, @samp{c[ad]\@{1,2\@}r} matches the strings @samp{car},
+@samp{cdr}, @samp{caar}, @samp{cadr}, @samp{cdar}, and @samp{cddr}, and
+nothing else.@*
+@samp{\@{0,1\@}} or @samp{\@{,1\@}} is equivalent to @samp{?}. @*
+@samp{\@{0,\@}} or @samp{\@{,\@}} is equivalent to @samp{*}. @*
+@samp{\@{1,\@}} is equivalent to @samp{+}.
@item \( @dots{} \)
@cindex @samp{(} in regexp
@enumerate
@item
-To enclose a set of @samp{\|} alternatives for other operations.
-Thus, @samp{\(foo\|bar\)x} matches either @samp{foox} or @samp{barx}.
+To enclose a set of @samp{\|} alternatives for other operations. Thus,
+the regular expression @samp{\(foo\|bar\)x} matches either @samp{foox}
+or @samp{barx}.
@item
-To enclose an expression for a suffix operator such as @samp{*} to act
-on. Thus, @samp{ba\(na\)*} matches @samp{bananana}, etc., with any
-(zero or more) number of @samp{na} strings.@refill
+To enclose a complicated expression for the postfix operators @samp{*},
+@samp{+} and @samp{?} to operate on. Thus, @samp{ba\(na\)*} matches
+@samp{ba}, @samp{bana}, @samp{banana}, @samp{bananana}, etc., with any
+number (zero or more) of @samp{na} strings.
@item
-To record a matched substring for future reference.
+To record a matched substring for future reference with
+@samp{\@var{digit}} (see below).
@end enumerate
This last application is not a consequence of the idea of a
-parenthetical grouping; it is a separate feature which happens to be
-assigned as a second meaning to the same @samp{\( @dots{} \)} construct
-because there is no conflict in practice between the two meanings.
-Here is an explanation of this feature:
+parenthetical grouping; it is a separate feature that was assigned as a
+second meaning to the same @samp{\( @dots{} \)} construct because, in
+practice, there was usually no conflict between the two meanings. But
+occasionally there is a conflict, and that led to the introduction of
+shy groups.
+
+@item \(?: @dots{} \)
+is the @dfn{shy group} construct. A shy group serves the first two
+purposes of an ordinary group (controlling the nesting of other
+operators), but it does not get a number, so you cannot refer back to
+its value with @samp{\@var{digit}}.
+
+Shy groups are particularly useful for mechanically-constructed regular
+expressions because they can be added automatically without altering the
+numbering of any ordinary, non-shy groups.
@item \@var{digit}
-matches the same text which matched the @var{digit}th occurrence of a
-@samp{\( @dots{} \)} construct.
+matches the same text that matched the @var{digit}th occurrence of a
+grouping (@samp{\( @dots{} \)}) construct.
-In other words, after the end of a @samp{\( @dots{} \)} construct. the
-matcher remembers the beginning and end of the text matched by that
-construct. Then, later on in the regular expression, you can use
-@samp{\} followed by @var{digit} to match that same text, whatever it
-may have been.
+In other words, after the end of a group, the matcher remembers the
+beginning and end of the text matched by that group. Later on in the
+regular expression you can use @samp{\} followed by @var{digit} to
+match that same text, whatever it may have been.
-The strings matching the first nine @samp{\( @dots{} \)} constructs
-appearing in a regular expression are assigned numbers 1 through 9 in
-the order that the open parentheses appear in the regular expression.
-So you can use @samp{\1} through @samp{\9} to refer to the text matched
-by the corresponding @samp{\( @dots{} \)} constructs.
+The strings matching the first nine grouping constructs appearing in
+the entire regular expression passed to a search or matching function
+are assigned numbers 1 through 9 in the order that the open
+parentheses appear in the regular expression. So you can use
+@samp{\1} through @samp{\9} to refer to the text matched by the
+corresponding grouping constructs.
For example, @samp{\(.*\)\1} matches any newline-free string that is
composed of two identical halves. The @samp{\(.*\)} matches the first
half, which may be anything, but the @samp{\1} that follows must match
the same exact text.
+If a @samp{\( @dots{} \)} construct matches more than once (which can
+happen, for instance, if it is followed by @samp{*}), only the last
+match is recorded.
+
+If a particular grouping construct in the regular expression was never
+matched---for instance, if it appears inside of an alternative that
+wasn't used, or inside of a repetition that repeated zero times---then
+the corresponding @samp{\@var{digit}} construct never matches
+anything. To use an artificial example,, @samp{\(foo\(b*\)\|lose\)\2}
+cannot match @samp{lose}: the second alternative inside the larger
+group matches it, but then @samp{\2} is undefined and can't match
+anything. But it can match @samp{foobb}, because the first
+alternative matches @samp{foob} and @samp{\2} matches @samp{b}.
+
@item \w
@cindex @samp{\w} in regexp
matches any word-constituent character. The editor syntax table
@item \W
@cindex @samp{\W} in regexp
-matches any character that is not a word-constituent.
+matches any character that is not a word constituent.
@item \s@var{code}
@cindex @samp{\s} in regexp
matches any character whose syntax is @var{code}. Here @var{code} is a
-character which represents a syntax code: thus, @samp{w} for word
+character that represents a syntax code: thus, @samp{w} for word
constituent, @samp{-} for whitespace, @samp{(} for open parenthesis,
-etc. @xref{Syntax Tables}, for a list of syntax codes and the
-characters that stand for them.
+etc. To represent whitespace syntax, use either @samp{-} or a space
+character. @xref{Syntax Class Table}, for a list of syntax codes and
+the characters that stand for them.
@item \S@var{code}
@cindex @samp{\S} in regexp
matches any character whose syntax is not @var{code}.
+
+@item \c@var{c}
+matches any character whose category is @var{c}. Here @var{c} is a
+character that represents a category: thus, @samp{c} for Chinese
+characters or @samp{g} for Greek characters in the standard category
+table.
+
+@item \C@var{c}
+matches any character whose category is not @var{c}.
@end table
- These regular expression constructs match the empty string---that is,
+ The following regular expression constructs match the empty string---that is,
they don't use up any characters---but whether they match depends on the
-context.
+context. For all, the beginning and end of the accessible portion of
+the buffer are treated as if they were the actual beginning and end of
+the buffer.
-@table @kbd
+@table @samp
@item \`
@cindex @samp{\`} in regexp
matches the empty string, but only at the beginning
@samp{foo} as a separate word. @samp{\bballs?\b} matches
@samp{ball} or @samp{balls} as a separate word.@refill
+@samp{\b} matches at the beginning or end of the buffer (or string)
+regardless of what text appears next to it.
+
@item \B
@cindex @samp{\B} in regexp
matches the empty string, but @emph{not} at the beginning or
-end of a word.
+end of a word, nor at the beginning or end of the buffer (or string).
@item \<
@cindex @samp{\<} in regexp
matches the empty string, but only at the beginning of a word.
+@samp{\<} matches at the beginning of the buffer (or string) only if a
+word-constituent character follows.
@item \>
@cindex @samp{\>} in regexp
-matches the empty string, but only at the end of a word.
+matches the empty string, but only at the end of a word. @samp{\>}
+matches at the end of the buffer (or string) only if the contents end
+with a word-constituent character.
+
+@item \_<
+@cindex @samp{\_<} in regexp
+matches the empty string, but only at the beginning of a symbol. A
+symbol is a sequence of one or more word or symbol constituent
+characters. @samp{\_<} matches at the beginning of the buffer (or
+string) only if a symbol-constituent character follows.
+
+@item \_>
+@cindex @samp{\_>} in regexp
+matches the empty string, but only at the end of a symbol. @samp{\_>}
+matches at the end of the buffer (or string) only if the contents end
+with a symbol-constituent character.
@end table
@kindex invalid-regexp
Not every string is a valid regular expression. For example, a string
-with unbalanced square brackets is invalid (with a few exceptions, such
-as @samp{[]]}, and so is a string that ends with a single @samp{\}. If
+that ends inside a character alternative without terminating @samp{]}
+is invalid, and so is a string that ends with a single @samp{\}. If
an invalid regular expression is passed to any of the search functions,
an @code{invalid-regexp} error is signaled.
-@defun regexp-quote string
-This function returns a regular expression string that matches exactly
-@var{string} and nothing else. This allows you to request an exact
-string match when calling a function that wants a regular expression.
-
-@example
-@group
-(regexp-quote "^The cat$")
- @result{} "\\^The cat\\$"
-@end group
-@end example
-
-One use of @code{regexp-quote} is to combine an exact string match with
-context described as a regular expression. For example, this searches
-for the string which is the value of @code{string}, surrounded by
-whitespace:
-
-@example
-@group
-(re-search-forward
- (concat "\\s " (regexp-quote string) "\\s "))
-@end group
-@end example
-@end defun
-
@node Regexp Example
@comment node-name, next, previous, up
@subsection Complex Regexp Example
- Here is a complicated regexp, used by Emacs to recognize the end of a
-sentence together with any whitespace that follows. It is the value of
-the variable @code{sentence-end}.
+ Here is a complicated regexp which was formerly used by Emacs to
+recognize the end of a sentence together with any whitespace that
+follows. (Nowadays Emacs uses a similar but more complex default
+regexp constructed by the function @code{sentence-end}.
+@xref{Standard Regexps}.)
First, we show the regexp as a string in Lisp syntax to distinguish
spaces from tab characters. The string constant begins and ends with a
tab and @samp{\n} for a newline.
@example
-"[.?!][]\"')@}]*\\($\\| $\\|\t\\| \\)[ \t\n]*"
+"[.?!][]\"')@}]*\\($\\| $\\|\t\\|@ @ \\)[ \t\n]*"
@end example
- In contrast, if you evaluate the variable @code{sentence-end}, you
-will see the following:
+@noindent
+In contrast, if you evaluate this string, you will see the following:
@example
@group
-sentence-end
-@result{}
-"[.?!][]\"')@}]*\\($\\| $\\| \\| \\)[
+"[.?!][]\"')@}]*\\($\\| $\\|\t\\|@ @ \\)[ \t\n]*"
+ @result{} "[.?!][]\"')@}]*\\($\\| $\\| \\|@ @ \\)[
]*"
@end group
@end example
@table @code
@item [.?!]
-The first part of the pattern consists of three characters, a period, a
-question mark and an exclamation mark, within square brackets. The
-match must begin with one of these three characters.
+The first part of the pattern is a character alternative that matches
+any one of three characters: period, question mark, and exclamation
+mark. The match must begin with one of these three characters. (This
+is one point where the new default regexp used by Emacs differs from
+the old. The new value also allows some non-@acronym{ASCII}
+characters that end a sentence without any following whitespace.)
@item []\"')@}]*
The second part of the pattern matches any closing braces and quotation
marks, zero or more of them, that may follow the period, question mark
or exclamation mark. The @code{\"} is Lisp syntax for a double-quote in
a string. The @samp{*} at the end indicates that the immediately
-preceding regular expression (a character set, in this case) may be
+preceding regular expression (a character alternative, in this case) may be
repeated zero or more times.
-@item \\($\\|@ \\|\t\\|@ @ \\)
+@item \\($\\|@ $\\|\t\\|@ @ \\)
The third part of the pattern matches the whitespace that follows the
-end of a sentence: the end of a line, or a tab, or two spaces. The
-double backslashes mark the parentheses and vertical bars as regular
-expression syntax; the parentheses mark the group and the vertical bars
-separate alternatives. The dollar sign is used to match the end of a
-line.
+end of a sentence: the end of a line (optionally with a space), or a
+tab, or two spaces. The double backslashes mark the parentheses and
+vertical bars as regular expression syntax; the parentheses delimit a
+group and the vertical bars separate alternatives. The dollar sign is
+used to match the end of a line.
@item [ \t\n]*
Finally, the last part of the pattern matches any additional whitespace
beyond the minimum needed to end a sentence.
@end table
+@node Regexp Functions
+@subsection Regular Expression Functions
+
+ These functions operate on regular expressions.
+
+@defun regexp-quote string
+This function returns a regular expression whose only exact match is
+@var{string}. Using this regular expression in @code{looking-at} will
+succeed only if the next characters in the buffer are @var{string};
+using it in a search function will succeed if the text being searched
+contains @var{string}.
+
+This allows you to request an exact string match or search when calling
+a function that wants a regular expression.
+
+@example
+@group
+(regexp-quote "^The cat$")
+ @result{} "\\^The cat\\$"
+@end group
+@end example
+
+One use of @code{regexp-quote} is to combine an exact string match with
+context described as a regular expression. For example, this searches
+for the string that is the value of @var{string}, surrounded by
+whitespace:
+
+@example
+@group
+(re-search-forward
+ (concat "\\s-" (regexp-quote string) "\\s-"))
+@end group
+@end example
+@end defun
+
+@defun regexp-opt strings &optional paren
+This function returns an efficient regular expression that will match
+any of the strings in the list @var{strings}. This is useful when you
+need to make matching or searching as fast as possible---for example,
+for Font Lock mode.
+
+If the optional argument @var{paren} is non-@code{nil}, then the
+returned regular expression is always enclosed by at least one
+parentheses-grouping construct. If @var{paren} is @code{words}, then
+that construct is additionally surrounded by @samp{\<} and @samp{\>}.
+
+This simplified definition of @code{regexp-opt} produces a
+regular expression which is equivalent to the actual value
+(but not as efficient):
+
+@example
+(defun regexp-opt (strings paren)
+ (let ((open-paren (if paren "\\(" ""))
+ (close-paren (if paren "\\)" "")))
+ (concat open-paren
+ (mapconcat 'regexp-quote strings "\\|")
+ close-paren)))
+@end example
+@end defun
+
+@defun regexp-opt-depth regexp
+This function returns the total number of grouping constructs
+(parenthesized expressions) in @var{regexp}. (This does not include
+shy groups.)
+@end defun
+
@node Regexp Search
@section Regular Expression Searching
@cindex regular expression searching
@cindex regexp searching
@cindex searching for regexp
- In GNU Emacs, you can search for the next match for a regexp either
-incrementally or not. For incremental search commands, see @ref{Regexp
-Search, , Regular Expression Search, emacs, The GNU Emacs Manual}. Here
-we describe only the search functions useful in programs. The principal
-one is @code{re-search-forward}.
+ In GNU Emacs, you can search for the next match for a regular
+expression either incrementally or not. For incremental search
+commands, see @ref{Regexp Search, , Regular Expression Search, emacs,
+The GNU Emacs Manual}. Here we describe only the search functions
+useful in programs. The principal one is @code{re-search-forward}.
+
+ These search functions convert the regular expression to multibyte if
+the buffer is multibyte; they convert the regular expression to unibyte
+if the buffer is unibyte. @xref{Text Representations}.
@deffn Command re-search-forward regexp &optional limit noerror repeat
This function searches forward in the current buffer for a string of
@var{regexp}, and leaves point at the end of the first match found.
It returns the new value of point.
-If @var{limit} is non-@code{nil} (it must be a position in the current
-buffer), then it is the upper bound to the search. No match extending
-after that position is accepted.
+If @var{limit} is non-@code{nil}, it must be a position in the current
+buffer. It specifies the upper bound to the search. No match
+extending after that position is accepted.
-What happens when the search fails depends on the value of
-@var{noerror}. If @var{noerror} is @code{nil}, a @code{search-failed}
-error is signaled. If @var{noerror} is @code{t},
-@code{re-search-forward} does nothing and returns @code{nil}. If
-@var{noerror} is neither @code{nil} nor @code{t}, then
-@code{re-search-forward} moves point to @var{limit} (or the end of the
-buffer) and returns @code{nil}.
+If @var{repeat} is supplied, it must be a positive number; the search
+is repeated that many times; each repetition starts at the end of the
+previous match. If all these successive searches succeed, the search
+succeeds, moving point and returning its new value. Otherwise the
+search fails. What @code{re-search-forward} does when the search
+fails depends on the value of @var{noerror}:
-If @var{repeat} is supplied (it must be a positive number), then the
-search is repeated that many times (each time starting at the end of the
-previous time's match). If these successive searches succeed, the
-function succeeds, moving point and returning its new value. Otherwise
-the search fails.
+@table @asis
+@item @code{nil}
+Signal a @code{search-failed} error.
+@item @code{t}
+Do nothing and return @code{nil}.
+@item anything else
+Move point to @var{limit} (or the end of the accessible portion of the
+buffer) and return @code{nil}.
+@end table
In the following example, point is initially before the @samp{T}.
Evaluating the search call moves point to the end of that line (between
text that is matched by the regular expression @var{regexp}, leaving
point at the beginning of the first text found.
-This function is analogous to @code{re-search-forward}, but they are
-not simple mirror images. @code{re-search-forward} finds the match
-whose beginning is as close as possible. If @code{re-search-backward}
-were a perfect mirror image, it would find the match whose end is as
-close as possible. However, in fact it finds the match whose beginning
-is as close as possible. The reason is that matching a regular
-expression at a given spot always works from beginning to end, and is
-done at a specified beginning position.
+This function is analogous to @code{re-search-forward}, but they are not
+simple mirror images. @code{re-search-forward} finds the match whose
+beginning is as close as possible to the starting point. If
+@code{re-search-backward} were a perfect mirror image, it would find the
+match whose end is as close as possible. However, in fact it finds the
+match whose beginning is as close as possible (and yet ends before the
+starting point). The reason for this is that matching a regular
+expression at a given spot always works from beginning to end, and
+starts at a specified beginning position.
A true mirror-image of @code{re-search-forward} would require a special
-feature for matching regexps from end to beginning. It's not worth the
-trouble of implementing that.
+feature for matching regular expressions from end to beginning. It's
+not worth the trouble of implementing that.
@end deffn
@defun string-match regexp string &optional start
@end example
@end defun
-@ignore
-@deffn Command delete-matching-lines regexp
-This function is identical to @code{delete-non-matching-lines}, save
-that it deletes what @code{delete-non-matching-lines} keeps.
+@defun looking-back regexp &optional limit
+This function returns @code{t} if @var{regexp} matches text before
+point, ending at point, and @code{nil} otherwise.
-In the example below, point is located on the first line of text.
+Because regular expression matching works only going forward, this is
+implemented by searching backwards from point for a match that ends at
+point. That can be quite slow if it has to search a long distance.
+You can bound the time required by specifying @var{limit}, which says
+not to search before @var{limit}. In this case, the match that is
+found must begin at or after @var{limit}.
@example
@group
---------- Buffer: foo ----------
-We hold these truths
-to be self-evident,
-that all men are created
-equal, and that they are
+I read "@point{}The cat in the hat
+comes back" twice.
---------- Buffer: foo ----------
-@end group
-@group
-(delete-matching-lines "the")
+(looking-back "read \"" 3)
+ @result{} t
+(looking-back "read \"" 4)
@result{} nil
-
----------- Buffer: foo ----------
-to be self-evident,
-that all men are created
----------- Buffer: foo ----------
@end group
@end example
-@end deffn
-
-@deffn Command flush-lines regexp
-This function is the same as @code{delete-matching-lines}.
-@end deffn
-
-@defun delete-non-matching-lines regexp
-This function deletes all lines following point which don't
-contain a match for the regular expression @var{regexp}.
@end defun
-@deffn Command keep-lines regexp
-This function is the same as @code{delete-non-matching-lines}.
-@end deffn
-
-@deffn Command how-many regexp
-This function counts the number of matches for @var{regexp} there are in
-the current buffer following point. It prints this number in
-the echo area, returning the string printed.
-@end deffn
-
-@deffn Command count-matches regexp
-This function is a synonym of @code{how-many}.
-@end deffn
-
-@deffn Command list-matching-lines regexp nlines
-This function is a synonym of @code{occur}.
-Show all lines following point containing a match for @var{regexp}.
-Display each line with @var{nlines} lines before and after,
-or @code{-}@var{nlines} before if @var{nlines} is negative.
-@var{nlines} defaults to @code{list-matching-lines-default-context-lines}.
-Interactively it is the prefix arg.
-
-The lines are shown in a buffer named @samp{*Occur*}.
-It serves as a menu to find any of the occurrences in this buffer.
-@kbd{C-h m} (@code{describe-mode} in that buffer gives help.
-@end deffn
-
-@defopt list-matching-lines-default-context-lines
-Default value is 0.
-Default number of context lines to include around a @code{list-matching-lines}
-match. A negative number means to include that many lines before the match.
-A positive number means to include that many lines both before and after.
-@end defopt
-@end ignore
-
-@node Search and Replace
-@section Search and Replace
-@cindex replacement
-
-@defun perform-replace from-string replacements query-flag regexp-flag delimited-flag &optional repeat-count map
-This function is the guts of @code{query-replace} and related commands.
-It searches for occurrences of @var{from-string} and replaces some or
-all of them. If @var{query-flag} is @code{nil}, it replaces all
-occurrences; otherwise, it asks the user what to do about each one.
-
-If @var{regexp-flag} is non-@code{nil}, then @var{from-string} is
-considered a regular expression; otherwise, it must match literally. If
-@var{delimited-flag} is non-@code{nil}, then only replacements
-surrounded by word boundaries are considered.
-
-The argument @var{replacements} specifies what to replace occurrences
-with. If it is a string, that string is used. It can also be a list of
-strings, to be used in cyclic order.
-
-If @var{repeat-count} is non-@code{nil}, it should be an integer, the
-number of occurrences to consider. In this case, @code{perform-replace}
-returns after considering that many occurrences.
-
-Normally, the keymap @code{query-replace-map} defines the possible user
-responses. The argument @var{map}, if non-@code{nil}, is a keymap to
-use instead of @code{query-replace-map}.
-@end defun
-
-@defvar query-replace-map
-This variable holds a special keymap that defines the valid user
-responses for @code{query-replace} and related functions, as well as
-@code{y-or-n-p} and @code{map-y-or-n-p}. It is unusual in two ways:
-
-@itemize @bullet
-@item
-The ``key bindings'' are not commands, just symbols that are meaningful
-to the functions that use this map.
-
-@item
-Prefix keys are not supported; each key binding must be for a single event
-key sequence. This is because the functions don't use read key sequence to
-get the input; instead, they read a single event and look it up ``by hand.''
-@end itemize
+@defvar search-spaces-regexp
+If this variable is non-@code{nil}, it should be a regular expression
+that says how to search for whitespace. In that case, any group of
+spaces in a regular expression being searched for stands for use of
+this regular expression. However, spaces inside of constructs such as
+@samp{[@dots{}]} and @samp{*}, @samp{+}, @samp{?} are not affected by
+@code{search-spaces-regexp}.
+
+Since this variable affects all regular expression search and match
+constructs, you should bind it temporarily for as small as possible
+a part of the code.
@end defvar
-Here are the meaningful ``bindings'' for @code{query-replace-map}.
-Several of them are meaningful only for @code{query-replace} and
-friends.
-
-@table @code
-@item act
-Do take the action being considered---in other words, ``yes.''
-
-@item skip
-Do not take action for this question---in other words, ``no.''
-
-@item exit
-Answer this question ``no,'' and don't ask any more.
-
-@item act-and-exit
-Answer this question ``yes,'' and don't ask any more.
-
-@item act-and-show
-Answer this question ``yes,'' but show the results---don't advance yet
-to the next question.
-
-@item automatic
-Answer this question and all subsequent questions in the series with
-``yes,'' without further user interaction.
-
-@item backup
-Move back to the previous place that a question was asked about.
-
-@item edit
-Enter a recursive edit to deal with this question---instead of any
-other action that would normally be taken.
-
-@item delete-and-edit
-Delete the text being considered, then enter a recursive edit to replace
-it.
+@node POSIX Regexps
+@section POSIX Regular Expression Searching
+
+ The usual regular expression functions do backtracking when necessary
+to handle the @samp{\|} and repetition constructs, but they continue
+this only until they find @emph{some} match. Then they succeed and
+report the first match found.
+
+ This section describes alternative search functions which perform the
+full backtracking specified by the POSIX standard for regular expression
+matching. They continue backtracking until they have tried all
+possibilities and found all matches, so they can report the longest
+match, as required by POSIX. This is much slower, so use these
+functions only when you really need the longest match.
+
+ The POSIX search and match functions do not properly support the
+non-greedy repetition operators. This is because POSIX backtracking
+conflicts with the semantics of non-greedy repetition.
+
+@defun posix-search-forward regexp &optional limit noerror repeat
+This is like @code{re-search-forward} except that it performs the full
+backtracking specified by the POSIX standard for regular expression
+matching.
+@end defun
-@item recenter
-Redisplay and center the window, then ask the same question again.
+@defun posix-search-backward regexp &optional limit noerror repeat
+This is like @code{re-search-backward} except that it performs the full
+backtracking specified by the POSIX standard for regular expression
+matching.
+@end defun
-@item quit
-Perform a quit right away. Only @code{y-or-n-p} and related functions
-use this answer.
+@defun posix-looking-at regexp
+This is like @code{looking-at} except that it performs the full
+backtracking specified by the POSIX standard for regular expression
+matching.
+@end defun
-@item help
-Display some help, then ask again.
-@end table
+@defun posix-string-match regexp string &optional start
+This is like @code{string-match} except that it performs the full
+backtracking specified by the POSIX standard for regular expression
+matching.
+@end defun
@node Match Data
@section The Match Data
@cindex match data
- Emacs keeps track of the positions of the start and end of segments of
-text found during a regular expression search. This means, for example,
-that you can search for a complex pattern, such as a date in an Rmail
-message, and then extract parts of the match under control of the
-pattern.
+ Emacs keeps track of the start and end positions of the segments of
+text found during a search; this is called the @dfn{match data}.
+Thanks to the match data, you can search for a complex pattern, such
+as a date in a mail message, and then extract parts of the match under
+control of the pattern.
Because the match data normally describe the most recent search only,
you must be careful not to do another search inadvertently between the
match data around it, to prevent it from being overwritten.
@menu
+* Replacing Match:: Replacing a substring that was matched.
* Simple Match Data:: Accessing single items of match data,
such as where a particular subexpression started.
-* Replacing Match:: Replacing a substring that was matched.
* Entire Match Data:: Accessing the entire match data at once, as a list.
* Saving Match Data:: Saving and restoring the match data.
@end menu
+@node Replacing Match
+@subsection Replacing the Text that Matched
+
+ This function replaces all or part of the text matched by the last
+search. It works by means of the match data.
+
+@cindex case in replacements
+@defun replace-match replacement &optional fixedcase literal string subexp
+This function replaces the text in the buffer (or in @var{string}) that
+was matched by the last search. It replaces that text with
+@var{replacement}.
+
+If you did the last search in a buffer, you should specify @code{nil}
+for @var{string} and make sure that the current buffer when you call
+@code{replace-match} is the one in which you did the searching or
+matching. Then @code{replace-match} does the replacement by editing
+the buffer; it leaves point at the end of the replacement text, and
+returns @code{t}.
+
+If you did the search in a string, pass the same string as @var{string}.
+Then @code{replace-match} does the replacement by constructing and
+returning a new string.
+
+If @var{fixedcase} is non-@code{nil}, then @code{replace-match} uses
+the replacement text without case conversion; otherwise, it converts
+the replacement text depending upon the capitalization of the text to
+be replaced. If the original text is all upper case, this converts
+the replacement text to upper case. If all words of the original text
+are capitalized, this capitalizes all the words of the replacement
+text. If all the words are one-letter and they are all upper case,
+they are treated as capitalized words rather than all-upper-case
+words.
+
+If @var{literal} is non-@code{nil}, then @var{replacement} is inserted
+exactly as it is, the only alterations being case changes as needed.
+If it is @code{nil} (the default), then the character @samp{\} is treated
+specially. If a @samp{\} appears in @var{replacement}, then it must be
+part of one of the following sequences:
+
+@table @asis
+@item @samp{\&}
+@cindex @samp{&} in replacement
+@samp{\&} stands for the entire text being replaced.
+
+@item @samp{\@var{n}}
+@cindex @samp{\@var{n}} in replacement
+@samp{\@var{n}}, where @var{n} is a digit, stands for the text that
+matched the @var{n}th subexpression in the original regexp.
+Subexpressions are those expressions grouped inside @samp{\(@dots{}\)}.
+If the @var{n}th subexpression never matched, an empty string is substituted.
+
+@item @samp{\\}
+@cindex @samp{\} in replacement
+@samp{\\} stands for a single @samp{\} in the replacement text.
+@end table
+
+These substitutions occur after case conversion, if any,
+so the strings they substitute are never case-converted.
+
+If @var{subexp} is non-@code{nil}, that says to replace just
+subexpression number @var{subexp} of the regexp that was matched, not
+the entire match. For example, after matching @samp{foo \(ba*r\)},
+calling @code{replace-match} with 1 as @var{subexp} means to replace
+just the text that matched @samp{\(ba*r\)}.
+@end defun
+
@node Simple Match Data
@subsection Simple Match Data Access
- This section explains how to use the match data to find the starting
-point or ending point of the text that was matched by a particular
-search, or by a particular parenthetical subexpression of a regular
-expression.
+ This section explains how to use the match data to find out what was
+matched by the last search or match operation, if it succeeded.
+
+ You can ask about the entire matching text, or about a particular
+parenthetical subexpression of a regular expression. The @var{count}
+argument in the functions below specifies which. If @var{count} is
+zero, you are asking about the entire match. If @var{count} is
+positive, it specifies which subexpression you want.
+
+ Recall that the subexpressions of a regular expression are those
+expressions grouped with escaped parentheses, @samp{\(@dots{}\)}. The
+@var{count}th subexpression is found by counting occurrences of
+@samp{\(} from the beginning of the whole regular expression. The first
+subexpression is numbered 1, the second 2, and so on. Only regular
+expressions can have subexpressions---after a simple string search, the
+only information available is about the entire match.
+
+ Every successful search sets the match data. Therefore, you should
+query the match data immediately after searching, before calling any
+other function that might perform another search. Alternatively, you
+may save and restore the match data (@pxref{Saving Match Data}) around
+the call to functions that could perform another search.
+
+ A search which fails may or may not alter the match data. In the
+past, a failing search did not do this, but we may change it in the
+future. So don't try to rely on the value of the match data after
+a failing search.
+
+@defun match-string count &optional in-string
+This function returns, as a string, the text matched in the last search
+or match operation. It returns the entire text if @var{count} is zero,
+or just the portion corresponding to the @var{count}th parenthetical
+subexpression, if @var{count} is positive.
+
+If the last such operation was done against a string with
+@code{string-match}, then you should pass the same string as the
+argument @var{in-string}. After a buffer search or match,
+you should omit @var{in-string} or pass @code{nil} for it; but you
+should make sure that the current buffer when you call
+@code{match-string} is the one in which you did the searching or
+matching.
+
+The value is @code{nil} if @var{count} is out of range, or for a
+subexpression inside a @samp{\|} alternative that wasn't used or a
+repetition that repeated zero times.
+@end defun
+
+@defun match-string-no-properties count &optional in-string
+This function is like @code{match-string} except that the result
+has no text properties.
+@end defun
@defun match-beginning count
This function returns the position of the start of text matched by the
last regular expression searched for, or a subexpression of it.
-The argument @var{count}, a number, specifies a subexpression whose
-start position is the value. If @var{count} is zero, then the value is
-the position of the text matched by the whole regexp. If @var{count} is
-greater than zero, then the value is the position of the beginning of
-the text matched by the @var{count}th subexpression.
+If @var{count} is zero, then the value is the position of the start of
+the entire match. Otherwise, @var{count} specifies a subexpression in
+the regular expression, and the value of the function is the starting
+position of the match for that subexpression.
-Subexpressions of a regular expression are those expressions grouped
-inside of parentheses, @samp{\(@dots{}\)}. The @var{count}th
-subexpression is found by counting occurrences of @samp{\(} from the
-beginning of the whole regular expression. The first subexpression is
-numbered 1, the second 2, and so on.
-
-The value is @code{nil} for a parenthetical grouping inside of a
-@samp{\|} alternative that wasn't used in the match.
+The value is @code{nil} for a subexpression inside a @samp{\|}
+alternative that wasn't used or a repetition that repeated zero times.
@end defun
@defun match-end count
-This function returns the position of the end of the text that matched
-the last regular expression searched for, or a subexpression of it.
-This function is otherwise similar to @code{match-beginning}.
+This function is like @code{match-beginning} except that it returns the
+position of the end of the match, rather than the position of the
+beginning.
@end defun
Here is an example of using the match data, with a comment showing the
@group
(string-match "\\(qu\\)\\(ick\\)"
"The quick fox jumped quickly.")
- ;0123456789
+ ;0123456789
@result{} 4
@end group
+@group
+(match-string 0 "The quick fox jumped quickly.")
+ @result{} "quick"
+(match-string 1 "The quick fox jumped quickly.")
+ @result{} "qu"
+(match-string 2 "The quick fox jumped quickly.")
+ @result{} "ick"
+@end group
+
@group
(match-beginning 1) ; @r{The beginning of the match}
@result{} 4 ; @r{with @samp{qu} is at index 4.}
(re-search-forward "The \\(cat \\)")
(match-beginning 0)
(match-beginning 1))
- @result{} (t 9 13)
+ @result{} (9 9 13)
@end group
@group
(In this case, the index returned is a buffer position; the first
character of the buffer counts as 1.)
-@node Replacing Match
-@subsection Replacing the Text That Matched
-
- This function replaces the text matched by the last search with
-@var{replacement}.
-
-@cindex case in replacements
-@defun replace-match replacement &optional fixedcase literal
-This function replaces the buffer text matched by the last search, with
-@var{replacement}. It applies only to buffers; you can't use
-@code{replace-match} to replace a substring found with
-@code{string-match}.
-
-If @var{fixedcase} is non-@code{nil}, then the case of the replacement
-text is not changed; otherwise, the replacement text is converted to a
-different case depending upon the capitalization of the text to be
-replaced. If the original text is all upper case, the replacement text
-is converted to upper case, except when all of the words in the original
-text are only one character long. In that event, the replacement text
-is capitalized. If @emph{any} of the words in the original text is
-capitalized, then all of the words in the replacement text are
-capitalized.
-
-If @var{literal} is non-@code{nil}, then @var{replacement} is inserted
-exactly as it is, the only alterations being case changes as needed.
-If it is @code{nil} (the default), then the character @samp{\} is treated
-specially. If a @samp{\} appears in @var{replacement}, then it must be
-part of one of the following sequences:
-
-@table @asis
-@item @samp{\&}
-@cindex @samp{&} in replacement
-@samp{\&} stands for the entire text being replaced.
-
-@item @samp{\@var{n}}
-@cindex @samp{\@var{n}} in replacement
-@samp{\@var{n}} stands for the text that matched the @var{n}th
-subexpression in the original regexp. Subexpressions are those
-expressions grouped inside of @samp{\(@dots{}\)}. @var{n} is a digit.
-
-@item @samp{\\}
-@cindex @samp{\} in replacement
-@samp{\\} stands for a single @samp{\} in the replacement text.
-@end table
-
-@code{replace-match} leaves point at the end of the replacement text,
-and returns @code{t}.
-@end defun
-
@node Entire Match Data
@subsection Accessing the Entire Match Data
The functions @code{match-data} and @code{set-match-data} read or
write the entire match data, all at once.
-@defun match-data
-This function returns a newly constructed list containing all the
-information on what text the last search matched. Element zero is the
-position of the beginning of the match for the whole expression; element
-one is the position of the end of the match for the expression. The
-next two elements are the positions of the beginning and end of the
-match for the first subexpression, and so on. In general, element
-@ifinfo
+@defun match-data &optional integers reuse reseat
+This function returns a list of positions (markers or integers) that
+record all the information on what text the last search matched.
+Element zero is the position of the beginning of the match for the
+whole expression; element one is the position of the end of the match
+for the expression. The next two elements are the positions of the
+beginning and end of the match for the first subexpression, and so on.
+In general, element
+@ifnottex
number 2@var{n}
-@end ifinfo
+@end ifnottex
@tex
number {\mathsurround=0pt $2n$}
@end tex
corresponds to @code{(match-beginning @var{n})}; and
element
-@ifinfo
+@ifnottex
number 2@var{n} + 1
-@end ifinfo
+@end ifnottex
@tex
number {\mathsurround=0pt $2n+1$}
@end tex
corresponds to @code{(match-end @var{n})}.
-All the elements are markers or @code{nil} if matching was done on a
-buffer, and all are integers or @code{nil} if matching was done on a
-string with @code{string-match}. (In Emacs 18 and earlier versions,
-markers were used even for matching on a string, except in the case
-of the integer 0.)
+Normally all the elements are markers or @code{nil}, but if
+@var{integers} is non-@code{nil}, that means to use integers instead
+of markers. (In that case, the buffer itself is appended as an
+additional element at the end of the list, to facilitate complete
+restoration of the match data.) If the last match was done on a
+string with @code{string-match}, then integers are always used,
+since markers can't point into a string.
+
+If @var{reuse} is non-@code{nil}, it should be a list. In that case,
+@code{match-data} stores the match data in @var{reuse}. That is,
+@var{reuse} is destructively modified. @var{reuse} does not need to
+have the right length. If it is not long enough to contain the match
+data, it is extended. If it is too long, the length of @var{reuse}
+stays the same, but the elements that were not used are set to
+@code{nil}. The purpose of this feature is to reduce the need for
+garbage collection.
+
+If @var{reseat} is non-@code{nil}, all markers on the @var{reuse} list
+are reseated to point to nowhere.
As always, there must be no possibility of intervening searches between
the call to a search function and the call to @code{match-data} that is
@end example
@end defun
-@defun set-match-data match-list
+@defun set-match-data match-list &optional reseat
This function sets the match data from the elements of @var{match-list},
which should be a list that was the value of a previous call to
-@code{match-data}.
+@code{match-data}. (More precisely, anything that has the same format
+will work.)
If @var{match-list} refers to a buffer that doesn't exist, you don't get
an error; that sets the match data in a meaningless but harmless way.
+If @var{reseat} is non-@code{nil}, all markers on the @var{match-list} list
+are reseated to point to nowhere.
+
@findex store-match-data
-@code{store-match-data} is an alias for @code{set-match-data}.
+@code{store-match-data} is a semi-obsolete alias for @code{set-match-data}.
@end defun
@node Saving Match Data
@subsection Saving and Restoring the Match Data
- All asynchronous process functions (filters and sentinels) and
-functions that use @code{recursive-edit} should save and restore the
-match data if they do a search or if they let the user type arbitrary
-commands. Saving the match data is useful in other cases as
-well---whenever you want to access the match data resulting from an
-earlier search, notwithstanding another intervening search.
-
- This example shows the problem that can arise if you fail to
-attend to this requirement:
+ When you call a function that may do a search, you may need to save
+and restore the match data around that call, if you want to preserve the
+match data from an earlier search for later use. Here is an example
+that shows the problem that arises if you fail to save the match data:
@example
@group
@end group
@end example
- In Emacs versions 19 and later, you can save and restore the match
-data with @code{save-match-data}:
+ You can save and restore the match data with @code{save-match-data}:
-@defspec save-match-data body@dots{}
-This special form executes @var{body}, saving and restoring the match
-data around it. This is useful if you wish to do a search without
-altering the match data that resulted from an earlier search.
-@end defspec
+@defmac save-match-data body@dots{}
+This macro executes @var{body}, saving and restoring the match
+data around it. The return value is the value of the last form in
+@var{body}.
+@end defmac
- You can use @code{set-match-data} together with @code{match-data} to
-imitate the effect of the special form @code{save-match-data}. This is
-useful for writing code that can run in Emacs 18. Here is how:
+ You could use @code{set-match-data} together with @code{match-data} to
+imitate the effect of the special form @code{save-match-data}. Here is
+how:
@example
@group
(let ((data (match-data)))
(unwind-protect
- @dots{} ; @r{May change the original match data.}
+ @dots{} ; @r{Ok to change the original match data.}
(set-match-data data)))
@end group
@end example
+ Emacs automatically saves and restores the match data when it runs
+process filter functions (@pxref{Filter Functions}) and process
+sentinels (@pxref{Sentinels}).
+
@ignore
Here is a function which restores the match data provided the buffer
associated with it still exists.
@end smallexample
@end ignore
-@node Searching and Case
-@section Searching and Case
-@cindex searching and case
+@node Search and Replace
+@section Search and Replace
+@cindex replacement
- By default, searches in Emacs ignore the case of the text they are
-searching through; if you specify searching for @samp{FOO}, then
-@samp{Foo} or @samp{foo} is also considered a match. Regexps, and in
-particular character sets, are included: thus, @samp{[aB]} would match
-@samp{a} or @samp{A} or @samp{b} or @samp{B}.
+ If you want to find all matches for a regexp in part of the buffer,
+and replace them, the best way is to write an explicit loop using
+@code{re-search-forward} and @code{replace-match}, like this:
- If you do not want this feature, set the variable
-@code{case-fold-search} to @code{nil}. Then all letters must match
-exactly, including case. This is a per-buffer-local variable; altering
-the variable affects only the current buffer. (@xref{Intro to
-Buffer-Local}.) Alternatively, you may change the value of
-@code{default-case-fold-search}, which is the default value of
-@code{case-fold-search} for buffers that do not override it.
+@example
+(while (re-search-forward "foo[ \t]+bar" nil t)
+ (replace-match "foobar"))
+@end example
- Note that the user-level incremental search feature handles case
-distinctions differently. When given a lower case letter, it looks for
-a match of either case, but when given an upper case letter, it looks
-for an upper case letter only. But this has nothing to do with the
-searching functions Lisp functions use.
+@noindent
+@xref{Replacing Match,, Replacing the Text that Matched}, for a
+description of @code{replace-match}.
+
+ However, replacing matches in a string is more complex, especially
+if you want to do it efficiently. So Emacs provides a function to do
+this.
+
+@defun replace-regexp-in-string regexp rep string &optional fixedcase literal subexp start
+This function copies @var{string} and searches it for matches for
+@var{regexp}, and replaces them with @var{rep}. It returns the
+modified copy. If @var{start} is non-@code{nil}, the search for
+matches starts at that index in @var{string}, so matches starting
+before that index are not changed.
+
+This function uses @code{replace-match} to do the replacement, and it
+passes the optional arguments @var{fixedcase}, @var{literal} and
+@var{subexp} along to @code{replace-match}.
+
+Instead of a string, @var{rep} can be a function. In that case,
+@code{replace-regexp-in-string} calls @var{rep} for each match,
+passing the text of the match as its sole argument. It collects the
+value @var{rep} returns and passes that to @code{replace-match} as the
+replacement string. The match-data at this point are the result
+of matching @var{regexp} against a substring of @var{string}.
+@end defun
-@defopt case-replace
-This variable determines whether @code{query-replace} should preserve
-case in replacements. If the variable is @code{nil}, then
-@code{replace-match} should not try to convert case.
-@end defopt
+ If you want to write a command along the lines of @code{query-replace},
+you can use @code{perform-replace} to do the work.
-@defopt case-fold-search
-This buffer-local variable determines whether searches should ignore
-case. If the variable is @code{nil} they do not ignore case; otherwise
-they do ignore case.
-@end defopt
+@defun perform-replace from-string replacements query-flag regexp-flag delimited-flag &optional repeat-count map start end
+This function is the guts of @code{query-replace} and related
+commands. It searches for occurrences of @var{from-string} in the
+text between positions @var{start} and @var{end} and replaces some or
+all of them. If @var{start} is @code{nil} (or omitted), point is used
+instead, and the end of the buffer's accessible portion is used for
+@var{end}.
-@defvar default-case-fold-search
-The value of this variable is the default value for
-@code{case-fold-search} in buffers that do not override it. This is the
-same as @code{(default-value 'case-fold-search)}.
+If @var{query-flag} is @code{nil}, it replaces all
+occurrences; otherwise, it asks the user what to do about each one.
+
+If @var{regexp-flag} is non-@code{nil}, then @var{from-string} is
+considered a regular expression; otherwise, it must match literally. If
+@var{delimited-flag} is non-@code{nil}, then only replacements
+surrounded by word boundaries are considered.
+
+The argument @var{replacements} specifies what to replace occurrences
+with. If it is a string, that string is used. It can also be a list of
+strings, to be used in cyclic order.
+
+If @var{replacements} is a cons cell, @code{(@var{function}
+. @var{data})}, this means to call @var{function} after each match to
+get the replacement text. This function is called with two arguments:
+@var{data}, and the number of replacements already made.
+
+If @var{repeat-count} is non-@code{nil}, it should be an integer. Then
+it specifies how many times to use each of the strings in the
+@var{replacements} list before advancing cyclically to the next one.
+
+If @var{from-string} contains upper-case letters, then
+@code{perform-replace} binds @code{case-fold-search} to @code{nil}, and
+it uses the @code{replacements} without altering the case of them.
+
+Normally, the keymap @code{query-replace-map} defines the possible
+user responses for queries. The argument @var{map}, if
+non-@code{nil}, specifies a keymap to use instead of
+@code{query-replace-map}.
+@end defun
+
+@defvar query-replace-map
+This variable holds a special keymap that defines the valid user
+responses for @code{perform-replace} and the commands that use it, as
+well as @code{y-or-n-p} and @code{map-y-or-n-p}. This map is unusual
+in two ways:
+
+@itemize @bullet
+@item
+The ``key bindings'' are not commands, just symbols that are meaningful
+to the functions that use this map.
+
+@item
+Prefix keys are not supported; each key binding must be for a
+single-event key sequence. This is because the functions don't use
+@code{read-key-sequence} to get the input; instead, they read a single
+event and look it up ``by hand.''
+@end itemize
@end defvar
+Here are the meaningful ``bindings'' for @code{query-replace-map}.
+Several of them are meaningful only for @code{query-replace} and
+friends.
+
+@table @code
+@item act
+Do take the action being considered---in other words, ``yes.''
+
+@item skip
+Do not take action for this question---in other words, ``no.''
+
+@item exit
+Answer this question ``no,'' and give up on the entire series of
+questions, assuming that the answers will be ``no.''
+
+@item act-and-exit
+Answer this question ``yes,'' and give up on the entire series of
+questions, assuming that subsequent answers will be ``no.''
+
+@item act-and-show
+Answer this question ``yes,'' but show the results---don't advance yet
+to the next question.
+
+@item automatic
+Answer this question and all subsequent questions in the series with
+``yes,'' without further user interaction.
+
+@item backup
+Move back to the previous place that a question was asked about.
+
+@item edit
+Enter a recursive edit to deal with this question---instead of any
+other action that would normally be taken.
+
+@item delete-and-edit
+Delete the text being considered, then enter a recursive edit to replace
+it.
+
+@item recenter
+Redisplay and center the window, then ask the same question again.
+
+@item quit
+Perform a quit right away. Only @code{y-or-n-p} and related functions
+use this answer.
+
+@item help
+Display some help, then ask again.
+@end table
+
@node Standard Regexps
@section Standard Regular Expressions Used in Editing
@cindex regexps used standardly in editing
used for certain purposes in editing:
@defvar page-delimiter
-This is the regexp describing line-beginnings that separate pages. The
-default value is @code{"^\014"} (i.e., @code{"^^L"} or @code{"^\C-l"}).
+This is the regular expression describing line-beginnings that separate
+pages. The default value is @code{"^\014"} (i.e., @code{"^^L"} or
+@code{"^\C-l"}); this matches a line that starts with a formfeed
+character.
@end defvar
+ The following two regular expressions should @emph{not} assume the
+match always starts at the beginning of a line; they should not use
+@samp{^} to anchor the match. Most often, the paragraph commands do
+check for a match only at the beginning of a line, which means that
+@samp{^} would be superfluous. When there is a nonzero left margin,
+they accept matches that start after the left margin. In that case, a
+@samp{^} would be incorrect. However, a @samp{^} is harmless in modes
+where a left margin is never used.
+
@defvar paragraph-separate
This is the regular expression for recognizing the beginning of a line
that separates paragraphs. (If you change this, you may have to
-change @code{paragraph-start} also.) The default value is @code{"^[
-\t\f]*$"}, which is a line that consists entirely of spaces, tabs, and
-form feeds.
+change @code{paragraph-start} also.) The default value is
+@w{@code{"[@ \t\f]*$"}}, which matches a line that consists entirely of
+spaces, tabs, and form feeds (after its left margin).
@end defvar
@defvar paragraph-start
This is the regular expression for recognizing the beginning of a line
that starts @emph{or} separates paragraphs. The default value is
-@code{"^[ \t\n\f]"}, which matches a line starting with a space, tab,
-newline, or form feed.
+@w{@code{"\f\\|[ \t]*$"}}, which matches a line containing only
+whitespace or starting with a form feed (after its left margin).
@end defvar
@defvar sentence-end
-This is the regular expression describing the end of a sentence. (All
-paragraph boundaries also end sentences, regardless.) The default value
-is:
-
-@example
-"[.?!][]\"')@}]*\\($\\|\t\\| \\)[ \t\n]*"
-@end example
+If non-@code{nil}, the value should be a regular expression describing
+the end of a sentence, including the whitespace following the
+sentence. (All paragraph boundaries also end sentences, regardless.)
+
+If the value is @code{nil}, the default, then the function
+@code{sentence-end} has to construct the regexp. That is why you
+should always call the function @code{sentence-end} to obtain the
+regexp to be used to recognize the end of a sentence.
+@end defvar
-This means a period, question mark or exclamation mark, followed by a
-closing brace, followed by tabs, spaces or new lines.
+@defun sentence-end
+This function returns the value of the variable @code{sentence-end},
+if non-@code{nil}. Otherwise it returns a default value based on the
+values of the variables @code{sentence-end-double-space}
+(@pxref{Definition of sentence-end-double-space}),
+@code{sentence-end-without-period} and
+@code{sentence-end-without-space}.
+@end defun
-For a detailed explanation of this regular expression, see @ref{Regexp
-Example}.
-@end defvar
+@ignore
+ arch-tag: c2573ca2-18aa-4839-93b8-924043ef831f
+@end ignore
HCoop / bpt / emacs.git / blobdiff