-@c -*-texinfo-*-
+@c -*- mode: texinfo; coding: utf-8 -*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1990-1995, 1998-1999, 2001-2015 Free Software
+@c Copyright (C) 1990-1995, 1998-1999, 2001-2016 Free Software
@c Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@node Strings and Characters
@end example
@end defun
-@defun substring string start &optional end
+@defun substring string &optional start end
This function returns a new string which consists of those characters
from @var{string} in the range from (and including) the character at the
index @var{start} up to (but excluding) the character at the index
-@var{end}. The first character is at index zero.
+@var{end}. The first character is at index zero. With one argument,
+this function just copies @var{string}.
@example
@group
@code{string-equal} is another name for @code{string=}.
@end defun
+@cindex locale-dependent string equivalence
@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
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
+dependent; a @var{locale} @code{"en_US.UTF-8"} is applicable on POSIX
+systems, while it would be, e.g., @code{"enu_USA.1252"} on MS-Windows
systems.
If @var{ignore-case} is non-@code{nil}, characters are converted to lower-case
before comparing them.
+@vindex w32-collate-ignore-punctuation
To emulate Unicode-compliant collation on MS-Windows systems,
bind @code{w32-collate-ignore-punctuation} to a non-@code{nil} value, since
-the codeset part of the locale cannot be "UTF-8" on MS-Windows.
+the codeset part of the locale cannot be @code{"UTF-8"} on MS-Windows.
If your system does not support a locale environment, this function
behaves like @code{string-equal}.
ignores case differences.
@end defun
-@cindex lexical comparison
+@cindex lexical comparison of strings
@defun string< string1 string2
@c (findex string< causes problems for permuted index!!)
This function compares two strings a character at a time. It
@end example
Symbols are also allowed as arguments, in which case their print names
-are used.
+are compared.
@end defun
@defun string-lessp string1 string2
@code{string-lessp} is another name for @code{string<}.
@end defun
+@defun string-greaterp string1 string2
+This function returns the result of comparing @var{string1} and
+@var{string2} in the opposite order, i.e., it is equivalent to calling
+@code{(string-lessp @var{string2} @var{string1})}.
+@end defun
+
+@cindex locale-dependent string comparison
@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
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}.
+For example, punctuation and whitespace characters might be ignored
+for sorting (@pxref{Sequence Functions}):
@example
@group
@end group
@end example
+This behavior is system-dependent; e.g., punctuation and whitespace
+are never ignored on Cygwin, regardless of locale.
+
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}:
+dependent; a @var{locale} @code{"en_US.UTF-8"} is applicable on POSIX
+systems, while it would be, e.g., @code{"enu_USA.1252"} on MS-Windows
+systems. The @var{locale} value of @code{"POSIX"} or @code{"C"} lets
+@code{string-collate-lessp} behave like @code{string-lessp}:
@example
@group
To emulate Unicode-compliant collation on MS-Windows systems,
bind @code{w32-collate-ignore-punctuation} to a non-@code{nil} value, since
-the codeset part of the locale cannot be "UTF-8" on MS-Windows.
+the codeset part of the locale cannot be @code{"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-version-lessp string1 string2
+This function compares strings lexicographically, except it treats
+sequences of numerical characters as if they comprised a base-ten
+number, and then compares the numbers. So @samp{foo2.png} is
+``smaller'' than @samp{foo12.png} according to this predicate, even if
+@samp{12} is lexicographically ``smaller'' than @samp{2}.
+@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
@var{start2} up to index @var{end2}.
The strings are compared by the numeric values of their characters.
-For instance, @var{str1} is considered ``smaller than'' @var{str2} if
+For instance, @var{str1} is considered less than @var{str2} if
its first differing character has a smaller numeric value. If
@var{ignore-case} is non-@code{nil}, characters are converted to
lower-case before comparing them. Unibyte strings are converted to
strings and integers. @code{format} (@pxref{Formatting Strings}) and
@code{prin1-to-string} (@pxref{Output Functions}) can also convert
Lisp objects into strings. @code{read-from-string} (@pxref{Input
-Functions}) can ``convert'' a string representation of a Lisp object
+Functions}) can convert a string representation of a Lisp object
into an object. The functions @code{string-to-multibyte} and
@code{string-to-unibyte} convert the text representation of a string
(@pxref{Converting Representations}).
Formatting is often useful for computing messages to be displayed. In
fact, the functions @code{message} and @code{error} provide the same
-formatting feature described here; they differ from @code{format} only
+formatting feature described here; they differ from @code{format-message} only
in how they use the result of formatting.
@defun format string &rest objects
if any.
@end defun
+@defun format-message string &rest objects
+@cindex curved quotes
+@cindex curly quotes
+This function acts like @code{format}, except it also converts any
+curved single quotes in @var{string} as per the value of
+@code{text-quoting-style}, and treats grave accent (@t{`}) and
+apostrophe (@t{'}) as if they were curved single quotes. @xref{Keys
+in Documentation}.
+@end defun
+
@cindex @samp{%} in format
@cindex format specification
A format specification is a sequence of characters beginning with a
Any other format character results in an @samp{Invalid format
operation} error.
- Here are several examples:
+ Here are several examples, which assume the typical
+@code{text-quoting-style} settings:
@example
@group
-(format "The name of this buffer is %s." (buffer-name))
- @result{} "The name of this buffer is strings.texi."
-
-(format "The buffer object prints as %s." (current-buffer))
- @result{} "The buffer object prints as strings.texi."
-
(format "The octal value of %d is %o,
and the hex value is %x." 18 18 18)
@result{} "The octal value of 18 is 22,
and the hex value is 12."
+
+(format-message
+ "The name of this buffer is ‘%s’." (buffer-name))
+ @result{} "The name of this buffer is ‘strings.texi’."
+
+(format-message
+ "The buffer object prints as `%s'." (current-buffer))
+ @result{} "The buffer object prints as ‘strings.texi’."
@end group
@end example
If the width is too small, @code{format} does not truncate the
object's printed representation. Thus, you can use a width to specify
a minimum spacing between columns with no risk of losing information.
-In the following three examples, @samp{%7s} specifies a minimum width
+In the following two examples, @samp{%7s} specifies a minimum width
of 7. In the first case, the string inserted in place of @samp{%7s}
has only 3 letters, and needs 4 blank spaces as padding. In the
second case, the string @code{"specification"} is 13 letters wide but
@example
@group
-(format "The word `%7s' has %d letters in it."
+(format "The word '%7s' has %d letters in it."
"foo" (length "foo"))
- @result{} "The word ` foo' has 3 letters in it."
-(format "The word `%7s' has %d letters in it."
+ @result{} "The word ' foo' has 3 letters in it."
+(format "The word '%7s' has %d letters in it."
"specification" (length "specification"))
- @result{} "The word `specification' has 13 letters in it."
+ @result{} "The word 'specification' has 13 letters in it."
@end group
@end example
ignored except for @samp{%d}, @samp{%e}, @samp{%f}, @samp{%g}, and if
both flags are used, @samp{+} takes precedence.
- The flag @samp{#} specifies an ``alternate form'' which depends on
+ The flag @samp{#} specifies an alternate form which depends on
the format in use. For @samp{%o}, it ensures that the result begins
with a @samp{0}. For @samp{%x} and @samp{%X}, it prefixes the result
with @samp{0x} or @samp{0X}. For @samp{%e}, @samp{%f}, and @samp{%g},
(format "%06d is padded on the left with zeros" 123)
@result{} "000123 is padded on the left with zeros"
-(format "%-6d is padded on the right" 123)
- @result{} "123 is padded on the right"
+(format "'%-6d' is padded on the right" 123)
+ @result{} "'123 ' is padded on the right"
-(format "The word `%-7s' actually has %d letters in it."
+(format "The word '%-7s' actually has %d letters in it."
"foo" (length "foo"))
- @result{} "The word `foo ' actually has 3 letters in it."
+ @result{} "The word 'foo ' actually has 3 letters in it."
@end group
@end example
Some language environments modify the case conversions of
@acronym{ASCII} characters; for example, in the Turkish language
-environment, the @acronym{ASCII} character @samp{I} is downcased into
-a Turkish ``dotless i''. This can interfere with code that requires
+environment, the @acronym{ASCII} capital I is downcased into
+a Turkish dotless i (@samp{ı}). This can interfere with code that requires
ordinary @acronym{ASCII} case conversion, such as implementations of
@acronym{ASCII}-based network protocols. In that case, use the
@code{with-case-table} macro with the variable @var{ascii-case-table},