@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999
-@c Free Software Foundation, Inc.
+@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2004
+@c Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@setfilename ../info/searching
@node Searching and Matching, Syntax Tables, Non-ASCII Characters, Top
* Regexp Search:: Searching for a match for a regexp.
* POSIX Regexps:: Searching POSIX-style for the longest match.
* 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.
+* Match Data:: Finding out which part of the text matched,
+ after a string or regexp search.
* Searching and Case:: Case-independent or case-significant searching.
* Standard Regexps:: Useful regexps for finding sentences, pages,...
@end menu
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, leaving point where it started.
+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.
@menu
* Syntax of Regexps:: Rules for writing regular expressions.
-* Regexp Functions:: Functions for operating on regular expressions.
* Regexp Example:: Illustrates regular expression syntax.
+* Regexp Functions:: Functions for operating on regular expressions.
@end menu
@node Syntax of Regexps
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
-Nested repetition operators can be extremely slow if they specify
-backtracking loops. For example, it could take hours for the regular
-expression @samp{\(x+y*\)*a} to try to match the sequence
-@samp{xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxz}, before it ultimately fails.
-The slowness is because Emacs must try each imaginable way of grouping
-the 35 @samp{x}s before concluding that none of them can work. To make
-sure your regular expressions run fast, check nested repetitions
+Nested repetition operators can be extremely slow or loop infinitely
+if they use repetition operators inside repetition operators. For
+example, it could take hours for the regular expression
+@samp{\(x+y*\)*a} to try to match the sequence
+@samp{xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxz}, 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.
@item @samp{+}
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 @sc{ascii} letter. Ranges may be
-intermixed freely with individual characters, as in @samp{[a-z$%.]},
-which matches any lower case @sc{ascii} letter or @samp{$}, @samp{%} or
-period.
+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
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-@sc{ascii} characters with the regular
+
+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-@sc{ascii} characters have codes
+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-@sc{ascii} characters (see below regarding @samp{^}),
+does match all non-@acronym{ASCII} characters (see below regarding @samp{^}),
in both multibyte and unibyte representations, because only the
-@sc{ascii} characters are excluded.
+@acronym{ASCII} characters are excluded.
-Starting in Emacs 21, a character alternative can also specify named
+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
@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} that 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.
@item @samp{$}
@cindex @samp{$} in regexp
@cindex end of line in regexp
-is similar to @samp{^} but matches only at the end of a line. Thus,
-@samp{x+$} matches a string of one @samp{x} or more at the end of a line.
+is similar to @samp{^} but matches only at the end of a line (or the
+end of the accessible portion of the buffer). Thus, @samp{x+$}
+matches a string of one @samp{x} or more at the end of a line.
When matching a string instead of a buffer, @samp{$} matches at the end
of the string or before a newline character.
@cindex character classes in regexp
Here is a table of the classes you can use in a character alternative,
-in Emacs 21, and what they mean:
+and what they mean:
@table @samp
@item [:ascii:]
-This matches any @sc{ascii} (unibyte) character.
+This matches any @acronym{ASCII} (unibyte) character.
@item [:alnum:]
This matches any letter or digit. (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 @sc{ascii} control character.
+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 @sc{ascii} control
+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 [:nonascii:]
-This matches any non-@sc{ascii} (multibyte) character.
+This matches any non-@acronym{ASCII} (multibyte) character.
@item [:print:]
-This matches printing characters---everything except @sc{ascii} control
+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
surrounding @samp{\( @dots{} \)} grouping can limit the grouping power of
@samp{\|}.@refill
-Full backtracking capability exists to handle multiple uses of
-@samp{\|}, if you use the POSIX regular expression functions
-(@pxref{POSIX Regexps}).
+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}
@samp{caaar}, @samp{cdddr}, @samp{cadar}, and so on.
@item \@{@var{m},@var{n}\@}
-is more general postfix operator that specifies repetition with a
+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.
This last application is not a consequence of the idea of a
parenthetical grouping; it is a separate feature that was assigned as a
second meaning to the same @samp{\( @dots{} \)} construct because, in
-pratice, there was usually no conflict between the two meanings. But
+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.
operators), but it does not get a number, so you cannot refer back to
its value with @samp{\@var{digit}}.
-Shy groups are particulary useful for mechanically-constructed regular
+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.
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 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 @samp
@item \`
@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
+@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 only if a
+@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. @samp{\>}
-matches at the end of the buffer only if the contents end with a
-word-constituent character.
+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
@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
-"[.?!][]\"')@}]*\\($\\| $\\|\t\\| \\)[ \t\n]*"
+"[.?!][]\"')@}]*\\($\\| $\\|\t\\|@ @ \\)[ \t\n]*"
@end example
@noindent
-In contrast, if you evaluate the variable @code{sentence-end}, you
-will see the following:
+In contrast, if you evaluate this string, you will see the following:
@example
@group
-sentence-end
- @result{} "[.?!][]\"')@}]*\\($\\| $\\| \\| \\)[
+"[.?!][]\"')@}]*\\($\\| $\\|\t\\|@ @ \\)[ \t\n]*"
+ @result{} "[.?!][]\"')@}]*\\($\\| $\\| \\|@ @ \\)[
]*"
@end group
@end example
@item [.?!]
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.
+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
@defun regexp-opt strings &optional paren
This function returns an efficient regular expression that will match
-any of the strings @var{strings}. This is useful when you need to make
-matching or searching as fast as possible---for example, for Font Lock
-mode.
+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.
+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
@defun regexp-opt-depth regexp
This function returns the total number of grouping constructs
-(parenthesized expressions) in @var{regexp}.
+(parenthesized expressions) in @var{regexp}. (This does not include
+shy groups.)
@end defun
@node Regexp Search
@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.
-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 all these successive searches succeed, the
-function succeeds, moving point and returning its new value. Otherwise
-the function fails.
+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
+function succeeds, moving point and returning its new value.
+Otherwise the function fails.
What happens when the function fails depends on the value of
@var{noerror}. If @var{noerror} is @code{nil}, a @code{search-failed}
@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}.
+accessible portion of the buffer) and returns @code{nil}.
In the following example, point is initially before the @samp{T}.
Evaluating the search call moves point to the end of that line (between
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. 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.
+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 regular expressions from end to beginning. It's
@end example
@end defun
+@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.
+
+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 ----------
+I read "@point{}The cat in the hat
+comes back" twice.
+---------- Buffer: foo ----------
+
+(looking-back "read \"" 3)
+ @result{} t
+(looking-back "read \"" 4)
+ @result{} nil
+@end group
+@end example
+@end defun
+
+@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
+
@node POSIX Regexps
@section POSIX Regular Expression Searching
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
@section Search and Replace
@cindex replacement
-@defun perform-replace from-string replacements start end query-flag regexp-flag delimited-flag &optional repeat-count map
+@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}, point is used instead, and
-the buffer's end is used for @var{end}.
+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}.
If @var{query-flag} is @code{nil}, it replaces all
occurrences; otherwise, it asks the user what to do about each one.
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 cyclicly to the next one.
+@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
Normally, the keymap @code{query-replace-map} defines the possible user
responses for queries. The argument @var{map}, if non-@code{nil}, is a
keymap to use instead of @code{query-replace-map}.
+
+@strong{Usage note:} Do not use this function in your own programs
+unless you want to do something very similar to what
+@code{query-replace} does, including setting the mark and possibly
+querying the user. For most purposes a simple loop like, for
+instance:
+
+@example
+(while (re-search-forward "foo[ \t]+bar" nil t)
+ (replace-match "foobar"))
+@end example
+
+@noindent
+is preferable. It runs faster and avoids side effects, such as
+setting the mark. @xref{Replacing Match,, Replacing the Text that
+Matched}, for a description of @code{replace-match}.
@end defun
@defvar query-replace-map
@cindex match data
Emacs keeps track of the start and end positions of the 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.
+text found during a 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.
Because the match data normally describe the most recent search only,
you must be careful not to do another search inadvertently between the
@var{replacement}.
If you did the last search in a buffer, you should specify @code{nil}
-for @var{string}. 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}.
+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
@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
@subsection Simple Match Data Access
This section explains how to use the match data to find out what was
-matched by the last search or match operation.
+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}
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.
+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
@group
(string-match "\\(qu\\)\\(ick\\)"
"The quick fox jumped quickly.")
- ;0123456789
+ ;0123456789
@result{} 4
@end group
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
+@defun match-data &optional integers reuse
+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 ifnottex
@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}.
+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.
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
@defmac save-match-data body@dots{}
This macro executes @var{body}, saving and restoring the match
-data around it.
+data around it. The return value is the value of the last form in
+@var{body}.
@end defmac
You could use @code{set-match-data} together with @code{match-data} to
searching functions used in Lisp code.
@defopt case-replace
-This variable determines whether the 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 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}.
@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
-@w{@code{"[@ \t\n\f]"}}, which matches a line starting with a space, tab,
-newline, or form feed (after its left margin).
+@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
-optionally by a closing parenthetical character, 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