Commit d3cb31cb authored by Michael Albinus's avatar Michael Albinus

* strings.texi (Text Comparison): Describe `string-collate-equalp'

and `string-collate-lessp'.
parent 6726de52
2014-09-07 Michael Albinus <michael.albinus@gmx.de>
* strings.texi (Text Comparison): Describe `string-collate-equalp'
and `string-collate-lessp'.
2014-09-06 Leo Liu <sdl.web@gmail.com>
* control.texi (Pattern matching case statement): Document vector
......
......@@ -458,6 +458,59 @@ Representations}.
@code{string-equal} is another name for @code{string=}.
@end defun
@defun string-collate-equalp string1 string2 &optional locale ignore-case
This function returns @code{t} if @var{string1} and @var{string2} are
equal with respect to collation rules. A collation rule is not only
determined by the lexicographic order of the characters contained in
@var{string1} and @var{string2}, but also further rules about
relations between these characters. Usually, it is defined by the
@var{locale} environment Emacs is running with.
For example, characters with different coding points but
the same meaning might be considered as equal, like different grave
accent Unicode characters:
@example
@group
(string-collate-equalp (string ?\uFF40) (string ?\u1FEF))
@result{} t
@end group
@end example
The optional argument @var{locale}, a string, overrides the setting of
your current locale identifier for collation. The value is system
dependent; a @var{locale} "en_US.UTF-8" is applicable on POSIX
systems, while it would be, e.g., "enu_USA.1252" on MS-Windows
systems.
If @var{IGNORE-CASE} is non-nil, characters are converted to lower-case
before comparing them.
To emulate Unicode-compliant collation on MS-Windows systems,
bind @code{w32-collate-ignore-punctuation} to a non-nil value, since
the codeset part of the locale cannot be "UTF-8" on MS-Windows.
If your system does not support a locale environment, this function
behaves like @code{string-equal}.
Do NOT use this function to compare file names for equality, only
for sorting them.
@end defun
@defun string-prefix-p string1 string2 &optional ignore-case
This function returns non-@code{nil} if @var{string1} is a prefix of
@var{string2}; i.e., if @var{string2} starts with @var{string1}. If
the optional argument @var{ignore-case} is non-@code{nil}, the
comparison ignores case differences.
@end defun
@defun string-suffix-p suffix string &optional ignore-case
This function returns non-@code{nil} if @var{suffix} is a suffix of
@var{string}; i.e., if @var{string} ends with @var{suffix}. If the
optional argument @var{ignore-case} is non-@code{nil}, the comparison
ignores case differences.
@end defun
@cindex lexical comparison
@defun string< string1 string2
@c (findex string< causes problems for permuted index!!)
......@@ -516,6 +569,50 @@ are used.
@code{string-lessp} is another name for @code{string<}.
@end defun
@defun string-collate-lessp string1 string2 &optional locale ignore-case
This function returns @code{t} if @var{string1} is less than
@var{string2} in collation order. A collation order is not only
determined by the lexicographic order of the characters contained in
@var{string1} and @var{string2}, but also further rules about
relations between these characters. Usually, it is defined by the
@var{locale} environment Emacs is running with.
For example, punctuation and whitespace characters might be considered
less significant for @ref{Sorting,,sorting}.
@example
@group
(sort '("11" "12" "1 1" "1 2" "1.1" "1.2") 'string-collate-lessp)
@result{} ("11" "1 1" "1.1" "12" "1 2" "1.2")
@end group
@end example
The optional argument @var{locale}, a string, overrides the setting of
your current locale identifier for collation. The value is system
dependent; a @var{locale} "en_US.UTF-8" is applicable on POSIX
systems, while it would be, e.g., "enu_USA.1252" on MS-Windows
systems. The @var{locale} "POSIX" lets @code{string-collate-lessp}
behave like @code{string-lessp}:
@example
@group
(sort '("11" "12" "1 1" "1 2" "1.1" "1.2")
(lambda (s1 s2) (string-collate-lessp s1 s2 "POSIX")))
@result{} ("1 1" "1 2" "1.1" "1.2" "11" "12")
@end group
@end example
If @var{IGNORE-CASE} is non-nil, characters are converted to lower-case
before comparing them.
To emulate Unicode-compliant collation on MS-Windows systems,
bind @code{w32-collate-ignore-punctuation} to a non-nil value, since
the codeset part of the locale cannot be "UTF-8" on MS-Windows.
If your system does not support a locale environment, this function
behaves like @code{string-lessp}.
@end defun
@defun string-prefix-p string1 string2 &optional ignore-case
This function returns non-@code{nil} if @var{string1} is a prefix of
@var{string2}; i.e., if @var{string2} starts with @var{string1}. If
......
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