X-Git-Url: https://code.delx.au/gnu-emacs/blobdiff_plain/a10f6c69acc8ff6f268352293a4cf3cd0f4e4563..171920a66145032a61fab9458ec6104000ff8dd8:/lispref/strings.texi

diff --git a/lispref/strings.texi b/lispref/strings.texi
index 1ca59d81f6..d0504684f8 100644
--- a/lispref/strings.texi
+++ b/lispref/strings.texi
@@ -1,6 +1,7 @@
 @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, 2003
+@c   Free Software Foundation, Inc.
 @c See the file elisp.texi for copying conditions.
 @setfilename ../info/strings
 @node Strings and Characters, Lists, Numbers, Top
@@ -13,8 +14,8 @@
 
   A string in Emacs Lisp is an array that contains an ordered sequence
 of characters.  Strings are used as names of symbols, buffers, and
-files, to send messages to users, to hold text being copied between
-buffers, and for many other purposes.  Because strings are so important,
+files; to send messages to users; to hold text being copied between
+buffers; and for many other purposes.  Because strings are so important,
 Emacs Lisp has many functions expressly for manipulating them.  Emacs
 Lisp programs use strings more often than individual characters.
 
@@ -25,57 +26,70 @@ keyboard character events.
 * Basics: String Basics.      Basic properties of strings and characters.
 * Predicates for Strings::    Testing whether an object is a string or char.
 * Creating Strings::          Functions to allocate new strings.
+* Modifying Strings::         Altering the contents of an existing string.
 * Text Comparison::           Comparing characters or strings.
-* String Conversion::         Converting characters or strings and vice versa.
-* Formatting Strings::        @code{format}: Emacs's analog of @code{printf}.
-* Character Case::            Case conversion functions.
-* Case Table::		      Customizing case conversion.
+* String Conversion::         Converting to and from characters and strings.
+* Formatting Strings::        @code{format}: Emacs's analogue of @code{printf}.
+* Case Conversion::           Case conversion functions.
+* Case Tables::		      Customizing case conversion.
 @end menu
 
 @node String Basics
 @section String and Character Basics
 
-  Strings in Emacs Lisp are arrays that contain an ordered sequence of
-characters.  Characters are represented in Emacs Lisp as integers;
-whether an integer was intended as a character or not is determined only
-by how it is used.  Thus, strings really contain integers.
-
-  The length of a string (like any array) is fixed and independent of
-the string contents, and cannot be altered.  Strings in Lisp are
-@emph{not} terminated by a distinguished character code.  (By contrast,
-strings in C are terminated by a character with @sc{ASCII} code 0.)
-This means that any character, including the null character (@sc{ASCII}
-code 0), is a valid element of a string.@refill
-
-  Since strings are considered arrays, you can operate on them with the
-general array functions.  (@xref{Sequences Arrays Vectors}.)  For
-example, you can access or change individual characters in a string
-using the functions @code{aref} and @code{aset} (@pxref{Array
-Functions}).
-
-  Each character in a string is stored in a single byte.  Therefore,
-numbers not in the range 0 to 255 are truncated when stored into a
-string.  This means that a string takes up much less memory than a
-vector of the same length.
+  Characters are represented in Emacs Lisp as integers;
+whether an integer is a character or not is determined only by how it is
+used.  Thus, strings really contain integers.
+
+  The length of a string (like any array) is fixed, and cannot be
+altered once the string exists.  Strings in Lisp are @emph{not}
+terminated by a distinguished character code.  (By contrast, strings in
+C are terminated by a character with @acronym{ASCII} code 0.)
+
+  Since strings are arrays, and therefore sequences as well, you can
+operate on them with the general array and sequence functions.
+(@xref{Sequences Arrays Vectors}.)  For example, you can access or
+change individual characters in a string using the functions @code{aref}
+and @code{aset} (@pxref{Array Functions}).
+
+  There are two text representations for non-@acronym{ASCII} characters in
+Emacs strings (and in buffers): unibyte and multibyte (@pxref{Text
+Representations}).  An @acronym{ASCII} character always occupies one byte in a
+string; in fact, when a string is all @acronym{ASCII}, there is no real
+difference between the unibyte and multibyte representations.
+For most Lisp programming, you don't need to be concerned with these two
+representations.
 
   Sometimes key sequences are represented as strings.  When a string is
 a key sequence, string elements in the range 128 to 255 represent meta
-characters (which are extremely large integers) rather than keyboard
-events in the range 128 to 255.
+characters (which are large integers) rather than character
+codes in the range 128 to 255.
 
   Strings cannot hold characters that have the hyper, super or alt
-modifiers; they can hold @sc{ASCII} control characters, but no other
-control characters.  They do not distinguish case in @sc{ASCII} control
-characters.  @xref{Character Type}, for more information about
-representation of meta and other modifiers for keyboard input
-characters.
+modifiers; they can hold @acronym{ASCII} control characters, but no other
+control characters.  They do not distinguish case in @acronym{ASCII} control
+characters.  If you want to store such characters in a sequence, such as
+a key sequence, you must use a vector instead of a string.
+@xref{Character Type}, for more information about the representation of meta
+and other modifiers for keyboard input characters.
+
+  Strings are useful for holding regular expressions.  You can also
+match regular expressions against strings with @code{string-match}
+(@pxref{Regexp Search}).  The functions @code{match-string}
+(@pxref{Simple Match Data}) and @code{replace-match} (@pxref{Replacing
+Match}) are useful for decomposing and modifying strings after
+matching regular expressions against them.
 
   Like a buffer, a string can contain text properties for the characters
 in it, as well as the characters themselves.  @xref{Text Properties}.
+All the Lisp primitives that copy text from strings to buffers or other
+strings also copy the properties of the characters being copied.
 
   @xref{Text}, for information about functions that display strings or
 copy them into buffers.  @xref{Character Type}, and @ref{String Type},
 for information about the syntax of characters and strings.
+@xref{Non-ASCII Characters}, for functions to convert between text
+representations and to encode and decode character codes.
 
 @node Predicates for Strings
 @section The Predicates for Strings
@@ -84,12 +98,12 @@ For more information about general sequence and array predicates,
 see @ref{Sequences Arrays Vectors}, and @ref{Arrays}.
 
 @defun stringp object
-  This function returns @code{t} if @var{object} is a string, @code{nil}
+This function returns @code{t} if @var{object} is a string, @code{nil}
 otherwise.
 @end defun
 
 @defun char-or-string-p object
-  This function returns @code{t} if @var{object} is a string or a
+This function returns @code{t} if @var{object} is a string or a
 character (i.e., an integer), @code{nil} otherwise.
 @end defun
 
@@ -100,7 +114,7 @@ character (i.e., an integer), @code{nil} otherwise.
 putting strings together, or by taking them apart.
 
 @defun make-string count character
-  This function returns a string made up of @var{count} repetitions of
+This function returns a string made up of @var{count} repetitions of
 @var{character}.  If @var{count} is negative, an error is signaled.
 
 @example
@@ -115,8 +129,17 @@ putting strings together, or by taking them apart.
 @code{make-list} (@pxref{Building Lists}).
 @end defun
 
+@defun string &rest characters
+This returns a string containing the characters @var{characters}.
+
+@example
+(string ?a ?b ?c)
+     @result{} "abc"
+@end example
+@end defun
+
 @defun substring string start &optional end
-  This function returns a new string which consists of those characters
+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.
@@ -136,7 +159,7 @@ position up to which the substring is copied.  The character whose index
 is 3 is actually the fourth character in the string.
 
 A negative number counts from the end of the string, so that @minus{}1
-signifies the index of the last character of the string.  For example: 
+signifies the index of the last character of the string.  For example:
 
 @example
 @group
@@ -150,7 +173,7 @@ In this example, the index for @samp{e} is @minus{}3, the index for
 @samp{f} is @minus{}2, and the index for @samp{g} is @minus{}1.
 Therefore, @samp{e} and @samp{f} are included, and @samp{g} is excluded.
 
-When @code{nil} is used as an index, it stands for the length of the
+When @code{nil} is used for @var{end}, it stands for the length of the
 string.  Thus,
 
 @example
@@ -175,10 +198,22 @@ of @var{string}.
 But we recommend @code{copy-sequence} for this purpose (@pxref{Sequence
 Functions}).
 
-A @code{wrong-type-argument} error is signaled if either @var{start} or
-@var{end} is not an integer or @code{nil}.  An @code{args-out-of-range}
-error is signaled if @var{start} indicates a character following
-@var{end}, or if either integer is out of range for @var{string}.
+If the characters copied from @var{string} have text properties, the
+properties are copied into the new string also.  @xref{Text Properties}.
+
+@code{substring} also accepts a vector for the first argument.
+For example:
+
+@example
+(substring [a b (c) "d"] 1 3)
+     @result{} [b (c)]
+@end example
+
+A @code{wrong-type-argument} error is signaled if @var{start} is not
+an integer or if @var{end} is neither an integer nor @code{nil}.  An
+@code{args-out-of-range} error is signaled if @var{start} indicates a
+character following @var{end}, or if either integer is out of range
+for @var{string}.
 
 Contrast this function with @code{buffer-substring} (@pxref{Buffer
 Contents}), which returns a string containing a portion of the text in
@@ -186,18 +221,27 @@ the current buffer.  The beginning of a string is at index 0, but the
 beginning of a buffer is at index 1.
 @end defun
 
+@defun substring-no-properties string &optional start end
+This works like @code{substring} but discards all text properties from
+the value.  Also, @var{start} may be omitted or @code{nil}, which is
+equivalent to 0.  Thus, @w{@code{(substring-no-properties
+@var{string})}} returns a copy of @var{string}, with all text
+properties removed.
+@end defun
+
 @defun concat &rest sequences
 @cindex copying strings
 @cindex concatenating strings
 This function returns a new string consisting of the characters in the
-arguments passed to it.  The arguments may be strings, lists of numbers,
-or vectors of numbers; they are not themselves changed.  If
-@code{concat} receives no arguments, it returns an empty string.
+arguments passed to it (along with their text properties, if any).  The
+arguments may be strings, lists of numbers, or vectors of numbers; they
+are not themselves changed.  If @code{concat} receives no arguments, it
+returns an empty string.
 
 @example
 (concat "abc" "-def")
      @result{} "abc-def"
-(concat "abc" (list 120 (+ 256 121)) [122])
+(concat "abc" (list 120 121) [122])
      @result{} "abcxyz"
 ;; @r{@code{nil} is an empty sequence.}
 (concat "abc" nil "-def")
@@ -209,36 +253,144 @@ or vectors of numbers; they are not themselves changed.  If
 @end example
 
 @noindent
-The second example above shows how characters stored in strings are
-taken modulo 256.  In other words, each character in the string is
-stored in one byte.
-
 The @code{concat} function always constructs a new string that is
 not @code{eq} to any existing string.
 
-When an argument is an integer (not a sequence of integers), it is
-converted to a string of digits making up the decimal printed
-representation of the integer.  @string{Don't use this feature---it
-exists for historical compatibility only, and we plan to change it by
-and by.}  If you wish to convert an integer to a decimal number in this
-way, use @code{format} (@pxref{Formatting Strings}) or
+In Emacs versions before 21, when an argument was an integer (not a
+sequence of integers), it was converted to a string of digits making up
+the decimal printed representation of the integer.  This obsolete usage
+no longer works.  The proper way to convert an integer to its decimal
+printed form is with @code{format} (@pxref{Formatting Strings}) or
 @code{number-to-string} (@pxref{String Conversion}).
 
-@example
-@group
-(concat 137)
-     @result{} "137"
-(concat 54 321)
-     @result{} "54321"
-@end group
-@end example
-
 For information about other concatenation functions, see the
 description of @code{mapconcat} in @ref{Mapping Functions},
-@code{vconcat} in @ref{Vectors}, and @code{append} in @ref{Building
+@code{vconcat} in @ref{Vector Functions}, and @code{append} in @ref{Building
 Lists}.
 @end defun
 
+@defun split-string string &optional separators omit-nulls
+This function splits @var{string} into substrings at matches for the
+regular expression @var{separators}.  Each match for @var{separators}
+defines a splitting point; the substrings between the splitting points
+are made into a list, which is the value returned by
+@code{split-string}.
+
+If @var{omit-nulls} is @code{nil}, the result contains null strings
+whenever there are two consecutive matches for @var{separators}, or a
+match is adjacent to the beginning or end of @var{string}.  If
+@var{omit-nulls} is @code{t}, these null strings are omitted from the
+result list.
+
+If @var{separators} is @code{nil} (or omitted),
+the default is the value of @code{split-string-default-separators}.
+
+As a special case, when @var{separators} is @code{nil} (or omitted),
+null strings are always omitted from the result.  Thus:
+
+@example
+(split-string "  two words ")
+     @result{} ("two" "words")
+@end example
+
+The result is not @samp{("" "two" "words" "")}, which would rarely be
+useful.  If you need such a result, use an explicit value for
+@var{separators}:
+
+@example
+(split-string "  two words "
+              split-string-default-separators)
+     @result{} ("" "two" "words" "")
+@end example
+
+More examples:
+
+@example
+(split-string "Soup is good food" "o")
+     @result{} ("S" "up is g" "" "d f" "" "d")
+(split-string "Soup is good food" "o" t)
+     @result{} ("S" "up is g" "d f" "d")
+(split-string "Soup is good food" "o+")
+     @result{} ("S" "up is g" "d f" "d")
+@end example
+
+Empty matches do count, except that @code{split-string} will not look
+for a final empty match when it already reached the end of the string
+using a non-empty match or when @var{string} is empty:
+
+@example
+(split-string "aooob" "o*")
+     @result{} ("" "a" "" "b" "")
+(split-string "ooaboo" "o*")
+     @result{} ("" "" "a" "b" "")
+(split-string "" "")
+     @result{} ("")
+@end example
+
+However, when @var{separators} can match the empty string,
+@var{omit-nulls} is usually @code{t}, so that the subtleties in the
+three previous examples are rarely relevant:
+
+@example
+(split-string "Soup is good food" "o*" t)
+     @result{} ("S" "u" "p" " " "i" "s" " " "g" "d" " " "f" "d")
+(split-string "Nice doggy!" "" t)
+     @result{} ("N" "i" "c" "e" " " "d" "o" "g" "g" "y" "!")
+(split-string "" "" t)
+     @result{} nil
+@end example
+
+Somewhat odd, but predictable, behavior can occur for certain
+``non-greedy'' values of @var{separators} that can prefer empty
+matches over non-empty matches.  Again, such values rarely occur in
+practice:
+
+@example
+(split-string "ooo" "o*" t)
+     @result{} nil
+(split-string "ooo" "\\|o+" t)
+     @result{} ("o" "o" "o")
+@end example
+@end defun
+
+@defvar split-string-default-separators
+The default value of @var{separators} for @code{split-string}.  Its
+usual value is @w{@samp{"[ \f\t\n\r\v]+"}}.
+@end defvar
+
+@node Modifying Strings
+@section Modifying Strings
+
+  The most basic way to alter the contents of an existing string is with
+@code{aset} (@pxref{Array Functions}).  @code{(aset @var{string}
+@var{idx} @var{char})} stores @var{char} into @var{string} at index
+@var{idx}.  Each character occupies one or more bytes, and if @var{char}
+needs a different number of bytes from the character already present at
+that index, @code{aset} signals an error.
+
+  A more powerful function is @code{store-substring}:
+
+@defun store-substring string idx obj
+This function alters part of the contents of the string @var{string}, by
+storing @var{obj} starting at index @var{idx}.  The argument @var{obj}
+may be either a character or a (smaller) string.
+
+Since it is impossible to change the length of an existing string, it is
+an error if @var{obj} doesn't fit within @var{string}'s actual length,
+or if any new character requires a different number of bytes from the
+character currently present at that point in @var{string}.
+@end defun
+
+  To clear out a string that contained a password, use
+@code{clear-string}:
+
+@defun clear-string string
+This clears the contents of @var{string} to zeros.
+It may also change @var{string}'s length and convert it to
+a unibyte string.
+@end defun
+
+@need 2000
 @node Text Comparison
 @section Comparison of Characters and Strings
 @cindex string equality
@@ -251,16 +403,17 @@ in case if @code{case-fold-search} is non-@code{nil}.
 @example
 (char-equal ?x ?x)
      @result{} t
-(char-to-string (+ 256 ?x))
-     @result{} "x"
-(char-equal ?x  (+ 256 ?x))
-     @result{} t
+(let ((case-fold-search nil))
+  (char-equal ?x ?X))
+     @result{} nil
 @end example
 @end defun
 
 @defun string= string1 string2
 This function returns @code{t} if the characters of the two strings
-match exactly; case is significant.
+match exactly.  Symbols are also allowed as arguments, in which case
+their print names are used.
+Case is always significant, regardless of @code{case-fold-search}.
 
 @example
 (string= "abc" "abc")
@@ -270,6 +423,26 @@ match exactly; case is significant.
 (string= "ab" "ABC")
      @result{} nil
 @end example
+
+The function @code{string=} ignores the text properties of the two
+strings.  When @code{equal} (@pxref{Equality Predicates}) compares two
+strings, it uses @code{string=}.
+
+For technical reasons, a unibyte and a multibyte string are
+@code{equal} if and only if they contain the same sequence of
+character codes and all these codes are either in the range 0 through
+127 (@acronym{ASCII}) or 160 through 255 (@code{eight-bit-graphic}).
+However, when a unibyte string gets converted to a multibyte string,
+all characters with codes in the range 160 through 255 get converted
+to characters with higher codes, whereas @acronym{ASCII} characters
+remain unchanged.  Thus, a unibyte string and its conversion to
+multibyte are only @code{equal} if the string is all @acronym{ASCII}.
+Character codes 160 through 255 are not entirely proper in multibyte
+text, even though they can occur.  As a consequence, the situation
+where a unibyte and a multibyte string are @code{equal} without both
+being all @acronym{ASCII} is a technical oddity that very few Emacs
+Lisp programmers ever get confronted with.  @xref{Text
+Representations}.
 @end defun
 
 @defun string-equal string1 string2
@@ -279,19 +452,21 @@ match exactly; case is significant.
 @cindex lexical comparison
 @defun string< string1 string2
 @c (findex string< causes problems for permuted index!!)
-This function compares two strings a character at a time.  First it
-scans both the strings at once to find the first pair of corresponding
-characters that do not match.  If the lesser character of those two is
+This function compares two strings a character at a time.  It
+scans both the strings at the same time to find the first pair of corresponding
+characters that do not match.  If the lesser character of these two is
 the character from @var{string1}, then @var{string1} is less, and this
 function returns @code{t}.  If the lesser character is the one from
 @var{string2}, then @var{string1} is greater, and this function returns
 @code{nil}.  If the two strings match entirely, the value is @code{nil}.
 
-Pairs of characters are compared by their @sc{ASCII} codes.  Keep in
-mind that lower case letters have higher numeric values in the
-@sc{ASCII} character set than their upper case counterparts; numbers and
+Pairs of characters are compared according to their character codes.
+Keep in mind that lower case letters have higher numeric values in the
+@acronym{ASCII} character set than their upper case counterparts; digits and
 many punctuation characters have a lower numeric value than upper case
-letters.
+letters.  An @acronym{ASCII} character is less than any non-@acronym{ASCII}
+character; a unibyte non-@acronym{ASCII} character is always less than any
+multibyte non-@acronym{ASCII} character (@pxref{Text Representations}).
 
 @example
 @group
@@ -320,13 +495,48 @@ no characters is less than any other string.
 (string< "abc" "ab")
      @result{} nil
 (string< "" "")
-     @result{} nil                   
+     @result{} nil
 @end group
 @end example
+
+Symbols are also allowed as arguments, in which case their print names
+are used.
 @end defun
 
 @defun string-lessp string1 string2
 @code{string-lessp} is another name for @code{string<}.
+@end defun
+
+@defun compare-strings string1 start1 end1 string2 start2 end2 &optional ignore-case
+This function compares the specified part of @var{string1} with the
+specified part of @var{string2}.  The specified part of @var{string1}
+runs from index @var{start1} up to index @var{end1} (@code{nil} means
+the end of the string).  The specified part of @var{string2} runs from
+index @var{start2} up to index @var{end2} (@code{nil} means the end of
+the string).
+
+The strings are both converted to multibyte for the comparison
+(@pxref{Text Representations}) so that a unibyte string and its
+conversion to multibyte are always regarded as equal.  If
+@var{ignore-case} is non-@code{nil}, then case is ignored, so that
+upper case letters can be equal to lower case letters.
+
+If the specified portions of the two strings match, the value is
+@code{t}.  Otherwise, the value is an integer which indicates how many
+leading characters agree, and which string is less.  Its absolute value
+is one plus the number of characters that agree at the beginning of the
+two strings.  The sign is negative if @var{string1} (or its specified
+portion) is less.
+@end defun
+
+@defun assoc-string key alist &optional case-fold
+This function works like @code{assoc}, except that @var{key} must be a
+string, and comparison is done using @code{compare-strings}.  If
+@var{case-fold} is non-@code{nil}, it ignores case differences.
+Unlike @code{assoc}, this function can also match elements of the alist
+that are strings rather than conses.  In particular, @var{alist} can
+be a list of strings rather than an actual alist.
+@xref{Association Lists}.
 @end defun
 
   See also @code{compare-buffer-substrings} in @ref{Comparing Text}, for
@@ -340,10 +550,13 @@ for a kind of string comparison; see @ref{Regexp Search}.
 @cindex conversion of strings
 
   This section describes functions for conversions between characters,
-strings and integers.  @code{format} and @code{prin1-to-string}
+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 into an object.
+string representation of a Lisp object into an object.  The functions
+@code{string-make-multibyte} and @code{string-make-unibyte} convert the
+text representation of a string (@pxref{Converting Representations}).
 
   @xref{Documentation}, for functions that produce textual descriptions
 of text characters and general input events
@@ -352,30 +565,16 @@ functions are used primarily for making help messages.
 
 @defun char-to-string character
 @cindex character to string
-  This function returns a new string with a length of one character.
-The value of @var{character}, modulo 256, is used to initialize the
-element of the string.
-
-This function is similar to @code{make-string} with an integer argument
-of 1.  (@xref{Creating Strings}.)  This conversion can also be done with
-@code{format} using the @samp{%c} format specification.
-(@xref{Formatting Strings}.)
-
-@example
-(char-to-string ?x)
-     @result{} "x"
-(char-to-string (+ 256 ?x))
-     @result{} "x"
-(make-string 1 ?x)
-     @result{} "x"
-@end example
+This function returns a new string containing one character,
+@var{character}.  This function is semi-obsolete because the function
+@code{string} is more general.  @xref{Creating Strings}.
 @end defun
 
 @defun string-to-char string
 @cindex string to character
   This function returns the first character in @var{string}.  If the
 string is empty, the function returns 0.  The value is also 0 when the
-first character of @var{string} is the null character, @sc{ASCII} code
+first character of @var{string} is the null character, @acronym{ASCII} code
 0.
 
 @example
@@ -385,8 +584,10 @@ first character of @var{string} is the null character, @sc{ASCII} code
      @result{} 120
 (string-to-char "")
      @result{} 0
+@group
 (string-to-char "\000")
      @result{} 0
+@end group
 @end example
 
 This function may be eliminated in the future if it does not seem useful
@@ -396,16 +597,18 @@ enough to retain.
 @defun number-to-string number
 @cindex integer to string
 @cindex integer to decimal
-This function returns a string consisting of the printed
+This function returns a string consisting of the printed base-ten
 representation of @var{number}, which may be an integer or a floating
-point number.  The value starts with a sign if the argument is
+point number.  The returned value starts with a minus sign if the argument is
 negative.
 
 @example
 (number-to-string 256)
      @result{} "256"
+@group
 (number-to-string -23)
      @result{} "-23"
+@end group
 (number-to-string -23.5)
      @result{} "-23.5"
 @end example
@@ -416,15 +619,25 @@ negative.
 See also the function @code{format} in @ref{Formatting Strings}.
 @end defun
 
-@defun string-to-number string
+@defun string-to-number string &optional base
 @cindex string to number
 This function returns the numeric value of the characters in
-@var{string}, read in base ten.  It skips spaces and tabs at the
-beginning of @var{string}, then reads as much of @var{string} as it can
-interpret as a number.  (On some systems it ignores other whitespace at
-the beginning, not just spaces and tabs.)  If the first character after
-the ignored whitespace is not a digit or a minus sign, this function
-returns 0.
+@var{string}.  If @var{base} is non-@code{nil}, it must be an integer
+between 2 and 16 (inclusive), and integers are converted in that base.
+If @var{base} is @code{nil}, then base ten is used.  Floating point
+conversion only works in base ten; we have not implemented other
+radices for floating point numbers, because that would be much more
+work and does not seem useful.  If @var{string} looks like an integer
+but its value is too large to fit into a Lisp integer,
+@code{string-to-number} returns a floating point result.
+
+The parsing skips spaces and tabs at the beginning of @var{string},
+then reads as much of @var{string} as it can interpret as a number in
+the given base.  (On some systems it ignores other whitespace at the
+beginning, not just spaces and tabs.)  If the first character after
+the ignored whitespace is neither a digit in the given base, nor a
+plus or minus sign, nor the leading dot of a floating point number,
+this function returns 0.
 
 @example
 (string-to-number "256")
@@ -435,12 +648,29 @@ returns 0.
      @result{} 0
 (string-to-number "-4.5")
      @result{} -4.5
+(string-to-number "1e5")
+     @result{} 100000.0
 @end example
 
 @findex string-to-int
 @code{string-to-int} is an obsolete alias for this function.
 @end defun
 
+  Here are some other functions that can convert to or from a string:
+
+@table @code
+@item concat
+@code{concat} can convert a vector or a list into a string.
+@xref{Creating Strings}.
+
+@item vconcat
+@code{vconcat} can convert a string into a vector.  @xref{Vector
+Functions}.
+
+@item append
+@code{append} can convert a string into a list.  @xref{Building Lists}.
+@end table
+
 @node Formatting Strings
 @comment  node-name,  next,  previous,  up
 @section Formatting Strings
@@ -448,8 +678,8 @@ returns 0.
 @cindex strings, formatting them
 
   @dfn{Formatting} means constructing a string by substitution of
-computed values at various places in a constant string.  This string
-controls how the other values are printed as well as where they appear;
+computed values at various places in a constant string.  This constant string
+controls how the other values are printed, as well as where they appear;
 it is called a @dfn{format string}.
 
   Formatting is often useful for computing messages to be displayed.  In
@@ -458,10 +688,14 @@ formatting feature described here; they differ from @code{format} only
 in how they use the result of formatting.
 
 @defun format string &rest objects
-  This function returns a new string that is made by copying
-@var{string} and then replacing any format specification 
+This function returns a new string that is made by copying
+@var{string} and then replacing any format specification
 in the copy with encodings of the corresponding @var{objects}.  The
 arguments @var{objects} are the computed values to be formatted.
+
+The characters in @var{string}, other than the format specifications,
+are copied directly into the output; if they have text properties,
+these are copied into the output also.
 @end defun
 
 @cindex @samp{%} in format
@@ -480,35 +714,36 @@ For example:
 @end example
 
   If @var{string} contains more than one format specification, the
-format specifications correspond with successive values from
+format specifications correspond to successive values from
 @var{objects}.  Thus, the first format specification in @var{string}
 uses the first such value, the second format specification uses the
 second such value, and so on.  Any extra format specifications (those
-for which there are no corresponding values) cause unpredictable
-behavior.  Any extra values to be formatted are ignored.
+for which there are no corresponding values) cause an error.  Any
+extra values to be formatted are ignored.
 
-  Certain format specifications require values of particular types.
-However, no error is signaled if the value actually supplied fails to
-have the expected type.  Instead, the output is likely to be
-meaningless.
+  Certain format specifications require values of particular types.  If
+you supply a value that doesn't fit the requirements, an error is
+signaled.
 
   Here is a table of valid format specifications:
 
 @table @samp
 @item %s
 Replace the specification with the printed representation of the object,
-made without quoting.  Thus, strings are represented by their contents
-alone, with no @samp{"} characters, and symbols appear without @samp{\}
-characters.
+made without quoting (that is, using @code{princ}, not
+@code{prin1}---@pxref{Output Functions}).  Thus, strings are represented
+by their contents alone, with no @samp{"} characters, and symbols appear
+without @samp{\} characters.
 
-If there is no corresponding object, the empty string is used.
+If the object is a string, its text properties are
+copied into the output.  The text properties of the @samp{%s} itself
+are also copied, but those of the object take priority.
 
 @item %S
 Replace the specification with the printed representation of the object,
-made with quoting.  Thus, strings are enclosed in @samp{"} characters,
-and @samp{\} characters appear where necessary before special characters.
-
-If there is no corresponding object, the empty string is used.
+made with quoting (that is, using @code{prin1}---@pxref{Output
+Functions}).  Thus, strings are enclosed in @samp{"} characters, and
+@samp{\} characters appear where necessary before special characters.
 
 @item %o
 @cindex integer to octal
@@ -520,9 +755,10 @@ Replace the specification with the base-ten representation of an
 integer.
 
 @item %x
+@itemx %X
 @cindex integer to hexadecimal
 Replace the specification with the base-sixteen representation of an
-integer.
+integer.  @samp{%x} uses lower case and @samp{%X} uses upper case.
 
 @item %c
 Replace the specification with the character which is the value given.
@@ -537,13 +773,13 @@ point number.
 
 @item %g
 Replace the specification with notation for a floating point number,
-using either exponential notation or decimal-point notation whichever
+using either exponential notation or decimal-point notation, whichever
 is shorter.
 
 @item %%
-A single @samp{%} is placed in the string.  This format specification is
-unusual in that it does not use a value.  For example, @code{(format "%%
-%d" 30)} returns @code{"% 30"}.
+Replace the specification with a single @samp{%}.  This format
+specification is unusual in that it does not use a value.  For example,
+@code{(format "%% %d" 30)} returns @code{"% 30"}.
 @end table
 
   Any other format character results in an @samp{Invalid format
@@ -557,26 +793,29 @@ operation} error.
      @result{} "The name of this buffer is strings.texi."
 
 (format "The buffer object prints as %s." (current-buffer))
-     @result{} "The buffer object prints as #<buffer strings.texi>."
+     @result{} "The buffer object prints as strings.texi."
 
-(format "The octal value of %d is %o, 
+(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, 
+     @result{} "The octal value of 18 is 22,
          and the hex value is 12."
 @end group
 @end example
 
-@cindex numeric prefix
 @cindex field width
 @cindex padding
-  All the specification characters allow an optional numeric prefix
-between the @samp{%} and the character.  The optional numeric prefix
-defines the minimum width for the object.  If the printed representation
-of the object contains fewer characters than this, then it is padded.
-The padding is on the left if the prefix is positive (or starts with
-zero) and on the right if the prefix is negative.  The padding character
-is normally a space, but if the numeric prefix starts with a zero, zeros
-are used for padding.
+  All the specification characters allow an optional ``width'', which
+is a digit-string between the @samp{%} and the character.  If the
+printed representation of the object contains fewer characters than
+this width, then it is padded.  The padding is on the left if the
+width is positive (or starts with zero) and on the right if the
+width is negative.  The padding character is normally a space, but if
+the width starts with a zero, zeros are used for padding.  Some of
+these conventions are ignored for specification characters for which
+they do not make sense.  That is, @samp{%s}, @samp{%S} and @samp{%c}
+accept a width starting with 0, but still pad with @emph{spaces} on
+the left.  Also, @samp{%%} accepts a width, but ignores it.  Here are
+some examples of padding:
 
 @example
 (format "%06d is padded on the left with zeros" 123)
@@ -586,10 +825,9 @@ are used for padding.
      @result{} "123    is padded on the right"
 @end example
 
-  @code{format} never truncates an object's printed representation, no
-matter what width you specify.  Thus, you can use a numeric prefix to
-specify a minimum spacing between columns with no risk of losing
-information.
+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
 of 7.  In the first case, the string inserted in place of @samp{%7s} has
@@ -597,41 +835,72 @@ only 3 letters, so 4 blank spaces are inserted for padding.  In the
 second case, the string @code{"specification"} is 13 letters wide but is
 not truncated.  In the third case, the padding is on the right.
 
-@smallexample 
+@smallexample
 @group
 (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
 
 @group
 (format "The word `%7s' actually has %d letters in it."
-        "specification" (length "specification")) 
-     @result{} "The word `specification' actually has 13 letters in it."  
+        "specification" (length "specification"))
+     @result{} "The word `specification' actually has 13 letters in it."
 @end group
 
 @group
 (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 smallexample
 
-@node Character Case
-@comment node-name, next, previous, up 
-@section Character Case
-@cindex upper case 
-@cindex lower case 
-@cindex character case 
+@cindex precision in format specifications
+  All the specification characters allow an optional ``precision''
+before the character (after the width, if present).  The precision is
+a decimal-point @samp{.} followed by a digit-string.  For the
+floating-point specifications (@samp{%e}, @samp{%f}, @samp{%g}), the
+precision specifies how many decimal places to show; if zero, the
+decimal-point itself is also omitted.  For @samp{%s} and @samp{%S},
+the precision truncates the string to the given width, so
+@samp{%.3s} shows only the first three characters of the
+representation for @var{object}.  Precision is ignored for other
+specification characters.
+
+@cindex flags in format specifications
+Immediately after the @samp{%} and before the optional width and
+precision, you can put certain ``flag'' characters.
+
+A space character inserts a space for positive numbers (otherwise
+nothing is inserted for positive numbers).  This flag is ignored
+except for @samp{%d}, @samp{%e}, @samp{%f}, @samp{%g}.
+
+The flag @samp{#} indicates ``alternate form''.  For @samp{%o} it
+ensures that the result begins with a 0.  For @samp{%x} and @samp{%X}
+the result is prefixed with @samp{0x} or @samp{0X}. For @samp{%e},
+@samp{%f}, and @samp{%g} a decimal point is always shown even if the
+precision is zero.
+
+@node Case Conversion
+@comment node-name, next, previous, up
+@section Case Conversion in Lisp
+@cindex upper case
+@cindex lower case
+@cindex character case
+@cindex case conversion in Lisp
 
   The character case functions change the case of single characters or
-of the contents of strings.  The functions convert only alphabetic
-characters (the letters @samp{A} through @samp{Z} and @samp{a} through
-@samp{z}); other characters are not altered.  The functions do not
-modify the strings that are passed to them as arguments.
+of the contents of strings.  The functions normally convert only
+alphabetic characters (the letters @samp{A} through @samp{Z} and
+@samp{a} through @samp{z}, as well as non-@acronym{ASCII} letters); other
+characters are not altered.  You can specify a different case
+conversion mapping by specifying a case table (@pxref{Case Tables}).
+
+  These functions do not modify the strings that are passed to them as
+arguments.
 
   The examples below use the characters @samp{X} and @samp{x} which have
-@sc{ASCII} codes 88 and 120 respectively.
+@acronym{ASCII} codes 88 and 120 respectively.
 
 @defun downcase string-or-char
 This function converts a character or a string to lower case.
@@ -663,7 +932,7 @@ lower case is converted to upper case.
 When the argument to @code{upcase} is a character, @code{upcase}
 returns the corresponding upper case character.  This value is an integer.
 If the original character is upper case, or is not a letter, then the
-value equals the original character.
+value returned equals the original character.
 
 @example
 (upcase "The cat in the hat")
@@ -685,17 +954,21 @@ case.
 
 The definition of a word is any sequence of consecutive characters that
 are assigned to the word constituent syntax class in the current syntax
-table (@xref{Syntax Class Table}).
+table (@pxref{Syntax Class Table}).
 
 When the argument to @code{capitalize} is a character, @code{capitalize}
 has the same result as @code{upcase}.
 
 @example
+@group
 (capitalize "The cat in the hat")
      @result{} "The Cat In The Hat"
+@end group
 
+@group
 (capitalize "THE 77TH-HATTED CAT")
      @result{} "The 77th-Hatted Cat"
+@end group
 
 @group
 (capitalize ?x)
@@ -704,57 +977,88 @@ has the same result as @code{upcase}.
 @end example
 @end defun
 
-@node Case Table
-@section The Case Table
+@defun upcase-initials string-or-char
+If @var{string-or-char} is a string, this function capitalizes the
+initials of the words in @var{string-or-char}, without altering any
+letters other than the initials.  It returns a new string whose
+contents are a copy of @var{string-or-char}, in which each word has
+had its initial letter converted to upper case.
 
-  You can customize case conversion by installing a special @dfn{case
-table}.  A case table specifies the mapping between upper case and lower
-case letters.  It affects both the string and character case conversion
-functions (see the previous section) and those that apply to text in the
-buffer (@pxref{Case Changes}).  You need a case table if you are using a
-language which has letters other than the standard @sc{ASCII} letters.
+The definition of a word is any sequence of consecutive characters that
+are assigned to the word constituent syntax class in the current syntax
+table (@pxref{Syntax Class Table}).
 
-  A case table is a list of this form:
+When the argument to @code{upcase-initials} is a character,
+@code{upcase-initials} has the same result as @code{upcase}.
 
 @example
-(@var{downcase} @var{upcase} @var{canonicalize} @var{equivalences})
+@group
+(upcase-initials "The CAT in the hAt")
+     @result{} "The CAT In The HAt"
+@end group
 @end example
+@end defun
 
-@noindent
-where each element is either @code{nil} or a string of length 256.  The
-element @var{downcase} says how to map each character to its lower-case
-equivalent.  The element @var{upcase} maps each character to its
-upper-case equivalent.  If lower and upper case characters are in
-one-to-one correspondence, use @code{nil} for @var{upcase}; then Emacs
-deduces the upcase table from @var{downcase}.
+  @xref{Text Comparison}, for functions that compare strings; some of
+them ignore case differences, or can optionally ignore case differences.
+
+@node Case Tables
+@section The Case Table
+
+  You can customize case conversion by installing a special @dfn{case
+table}.  A case table specifies the mapping between upper case and lower
+case letters.  It affects both the case conversion functions for Lisp
+objects (see the previous section) and those that apply to text in the
+buffer (@pxref{Case Changes}).  Each buffer has a case table; there is
+also a standard case table which is used to initialize the case table
+of new buffers.
+
+  A case table is a char-table (@pxref{Char-Tables}) whose subtype is
+@code{case-table}.  This char-table maps each character into the
+corresponding lower case character.  It has three extra slots, which
+hold related tables:
+
+@table @var
+@item upcase
+The upcase table maps each character into the corresponding upper
+case character.
+@item canonicalize
+The canonicalize table maps all of a set of case-related characters
+into a particular member of that set.
+@item equivalences
+The equivalences table maps each one of a set of case-related characters
+into the next character in that set.
+@end table
+
+  In simple cases, all you need to specify is the mapping to lower-case;
+the three related tables will be calculated automatically from that one.
 
   For some languages, upper and lower case letters are not in one-to-one
 correspondence.  There may be two different lower case letters with the
 same upper case equivalent.  In these cases, you need to specify the
-maps for both directions.
+maps for both lower case and upper case.
 
-  The element @var{canonicalize} maps each character to a canonical
+  The extra table @var{canonicalize} maps each character to a canonical
 equivalent; any two characters that are related by case-conversion have
-the same canonical equivalent character.
+the same canonical equivalent character.  For example, since @samp{a}
+and @samp{A} are related by case-conversion, they should have the same
+canonical equivalent character (which should be either @samp{a} for both
+of them, or @samp{A} for both of them).
 
-  The element @var{equivalences} is a map that cyclicly permutes each
-equivalence class (of characters with the same canonical equivalent).
-(For ordinary @sc{ASCII}, this would map @samp{a} into @samp{A} and
-@samp{A} into @samp{a}, and likewise for each set of equivalent
-characters.)
+  The extra table @var{equivalences} is a map that cyclically permutes
+each equivalence class (of characters with the same canonical
+equivalent).  (For ordinary @acronym{ASCII}, this would map @samp{a} into
+@samp{A} and @samp{A} into @samp{a}, and likewise for each set of
+equivalent characters.)
 
   When you construct a case table, you can provide @code{nil} for
-@var{canonicalize}; then Emacs fills in this string from @var{upcase}
-and @var{downcase}.  You can also provide @code{nil} for
-@var{equivalences}; then Emacs fills in this string from
+@var{canonicalize}; then Emacs fills in this slot from the lower case
+and upper case mappings.  You can also provide @code{nil} for
+@var{equivalences}; then Emacs fills in this slot from
 @var{canonicalize}.  In a case table that is actually in use, those
 components are non-@code{nil}.  Do not try to specify @var{equivalences}
 without also specifying @var{canonicalize}.
 
-  Each buffer has a case table.  Emacs also has a @dfn{standard case
-table} which is copied into each buffer when you create the buffer.
-Changing the standard case table doesn't affect any existing buffers.
-
   Here are the functions for working with case tables:
 
 @defun case-table-p object
@@ -764,7 +1068,7 @@ table.
 
 @defun set-standard-case-table table
 This function makes @var{table} the standard case table, so that it will
-apply to any buffers created subsequently.
+be used in any buffers created subsequently.
 @end defun
 
 @defun standard-case-table
@@ -780,22 +1084,22 @@ This sets the current buffer's case table to @var{table}.
 @end defun
 
   The following three functions are convenient subroutines for packages
-that define non-@sc{ASCII} character sets.  They modify a string
-@var{downcase-table} provided as an argument; this should be a string to
-be used as the @var{downcase} part of a case table.  They also modify
-the standard syntax table.  @xref{Syntax Tables}.
+that define non-@acronym{ASCII} character sets.  They modify the specified
+case table @var{case-table}; they also modify the standard syntax table.
+@xref{Syntax Tables}.  Normally you would use these functions to change
+the standard case table.
 
-@defun set-case-syntax-pair uc lc downcase-table
+@defun set-case-syntax-pair uc lc case-table
 This function specifies a pair of corresponding letters, one upper case
 and one lower case.
 @end defun
 
-@defun set-case-syntax-delims l r downcase-table
+@defun set-case-syntax-delims l r case-table
 This function makes characters @var{l} and @var{r} a matching pair of
 case-invariant delimiters.
 @end defun
 
-@defun set-case-syntax char syntax downcase-table
+@defun set-case-syntax char syntax case-table
 This function makes @var{char} case-invariant, with syntax
 @var{syntax}.
 @end defun
@@ -805,7 +1109,6 @@ This command displays a description of the contents of the current
 buffer's case table.
 @end deffn
 
-@cindex ISO Latin 1
-@pindex iso-syntax
-You can load the library @file{iso-syntax} to set up the standard syntax
-table and define a case table for the 8-bit ISO Latin 1 character set.
+@ignore
+   arch-tag: 700b8e95-7aa5-4b52-9eb3-8f2e1ea152b4
+@end ignore