Changes to m4/doc/m4.texinfo,v [branch-1_4]

[Eric Blake]

CVSROOT:        /sources/m4
Module name:    m4
Branch:         branch-1_4
Changes by:     Eric Blake <ericb>      07/03/01 21:46:05

Index: doc/m4.texinfo
===================================================================
RCS file: /sources/m4/m4/doc/m4.texinfo,v
retrieving revision 1.1.1.1.2.118
retrieving revision 1.1.1.1.2.119
diff -u -b -r1.1.1.1.2.118 -r1.1.1.1.2.119
--- doc/m4.texinfo      28 Feb 2007 21:51:36 -0000      1.1.1.1.2.118
+++ doc/m4.texinfo      1 Mar 2007 21:46:05 -0000       1.1.1.1.2.119
@@ -275,8 +275,8 @@
 
 Indices of concepts and macros
 
-* Concept index::               Index for many concepts
 * Macro index::                 Index for all @code{m4} macros
+* Concept index::               Index for many concepts
 
 @end detailmenu
 @end menu
@@ -302,6 +302,7 @@
 @node Intro
 @section Introduction to @code{m4}
 
address@hidden overview of @code{m4}
 @code{m4} is a macro processor, in the sense that it copies its
 input to the output, expanding macros as it goes.  Macros are either
 builtin or user-defined, and can take any number of arguments.
@@ -333,6 +334,8 @@
 @node History
 @section Historical references
 
address@hidden history of @code{m4}
address@hidden @acronym{GNU} M4, history of
 @code{GPM} was an important ancestor of @code{m4}.  See
 C. Stratchey: ``A General Purpose Macro generator'', Computer Journal
 8,3 (1965), pp. 225 ff.  @code{GPM} is also succinctly described into
@@ -391,6 +394,9 @@
 @node Bugs
 @section Problems and bugs
 
address@hidden reporting bugs
address@hidden bug reports
address@hidden suggestions, reporting
 If you have problems with @acronym{GNU} M4 or think you've found a bug,
 please report it.  Before reporting a bug, make sure you've actually
 found a real bug.  Carefully reread the documentation and see if it
@@ -417,6 +423,7 @@
 @node Manual
 @section Using this manual
 
address@hidden examples, understanding
 This manual contains a number of examples of @code{m4} input and output,
 and a simple notation is used to distinguish input, output and error
 messages from @code{m4}.  Examples are set out from the normal text, and
@@ -486,6 +493,8 @@
 @node Invoking m4
 @chapter Invoking @code{m4}
 
address@hidden command line
address@hidden invoking @code{m4}
 The format of the @code{m4} command is:
 
 @comment ignore
@@ -552,6 +561,8 @@
 
 @item -E
 @itemx --fatal-warnings
address@hidden errors, fatal
address@hidden fatal errors
 Controls the effect of warnings.  If unspecified, then execution
 continues and exit status is unaffected when a warning is printed.  If
 specified exactly once, warnings become fatal; when one is issued,
@@ -610,6 +621,7 @@
 
 @cindex macro definitions, on the command line
 @cindex command line, macro definitions on the
address@hidden preprocessor features
 Several options allow @code{m4} to behave more like a preprocessor.
 Macro definitions and deletions can be made on the command line, the
 search path can be altered, and the output file can track where the
@@ -633,6 +645,9 @@
 
 @item -s
 @itemx --synclines
address@hidden syncronization lines
address@hidden location, input
address@hidden input location
 Generate synchronization lines, for use by the C preprocessor or other
 similar tools.  Order is significant with respect to file names.  This
 option is useful, for example, when @code{m4} is used as a
@@ -682,6 +697,8 @@
 
 @item -L @var{NUM}
 @itemx address@hidden
address@hidden nesting limit
address@hidden limit, nesting
 Artificially limit the nesting of macro calls to @var{NUM} levels,
 stopping program execution if this limit is ever exceeded.  When not
 specified, nesting is limited to 1024 levels.  A value of zero means
@@ -694,6 +711,7 @@
 Most users would never need this option.  If shown to be obtrusive,
 this option (which is still experimental) might well disappear.
 
address@hidden rescanning
 This option does @emph{not} have the ability to break endless
 rescanning loops, since these do not necessarily consume much memory
 or stack space.  Through clever usage of rescanning loops, one can
@@ -844,6 +862,7 @@
 @section Macro names
 
 @cindex names
address@hidden words
 A name is any sequence of letters, digits, and the character @samp{_}
 (underscore), where the first character is not a digit.  @code{m4} will
 use the longest such sequence found in the input.  If a name has a
@@ -856,6 +875,7 @@
 @section Quoting input to @code{m4}
 
 @cindex quoted string
address@hidden string, quoted
 A quoted string is a sequence of characters surrounded by quote
 strings, defaulting to
 @samp{`} and @samp{'}, where the nested begin and end quotes within the
@@ -907,6 +927,7 @@
 @node Other tokens
 @section Other kinds of input tokens
 
address@hidden tokens, special
 Any character, that is neither a part of a name, nor of a quoted string,
 nor a comment, is a token by itself.  When not in the context of macro
 expansion, all of these tokens are just copied to output.  However,
@@ -1114,6 +1135,7 @@
 @section Macro invocation
 
 @cindex macro invocation
address@hidden invoking macros
 Macro invocations has one of the forms
 
 @comment ignore
@@ -1235,6 +1257,7 @@
 the @code{divert} builtin macro will be called, which expands to the
 empty string.
 
address@hidden rescanning
 The output of macro evaluations is always rescanned.  The following
 example would yield the string @samp{de}, exactly as if @code{m4}
 has been given @address@hidden(`abcde', `3', `2')}} as input:
@@ -1316,6 +1339,8 @@
 @result{}
 @end example
 
address@hidden warnings, suppressing
address@hidden suppressing warnings
 Normally @code{m4} will issue warnings if a builtin macro is called
 with an inappropriate number of arguments, but it can be suppressed with
 the @option{--quiet} command line option (or @option{--silent}, or
@@ -1392,6 +1417,8 @@
 foo(`() (() (')
 @end example
 
address@hidden quoting rule of thumb
address@hidden rule of thumb, quoting
 It is, however, in certain cases necessary (because nested expansion
 must occur to create the arguments for the outer macro) or convenient
 (because it uses fewer characters) to leave out quotes for some
@@ -1526,7 +1553,15 @@
 (@pxref{Indir}) and @code{defn} (@pxref{Defn}).
 
 @cindex arrays
-Arrays and associative arrays can be simulated by using this trick.
+Arrays and associative arrays can be simulated by using non-standard
+macro names.
+
address@hidden Composite array (@var{index})
address@hidden Composite array_set (@var{index}, @ovar{value})
+Provide access to entries within an array.  @code{array} reads the entry
+at location @var{index}, and @code{array_set} assigns @var{value} to
+location @var{index}.
address@hidden deffn
 
 @example
 define(`array', `defn(format(``array[%d]'', `$1'))')
@@ -1549,13 +1584,18 @@
 @section Arguments to macros
 
 @cindex macros, arguments to
address@hidden Arguments to macros
address@hidden arguments to macros
 Macros can have arguments.  The @var{n}th argument is denoted by
 @code{$n} in the expansion text, and is replaced by the @var{n}th actual
 argument, when the macro is expanded.  Replacement of arguments happens
 before rescanning, regardless of how many nesting levels of quoting
 appear in the expansion.  Here is an example of a macro with
-two arguments.  It simply exchanges the order of the two arguments.
+two arguments.
+
address@hidden Composite exch (@var{arg1}, @var{arg2})
+Expands to @var{arg2} followed by @var{arg1}, effectively exchanging
+their order.
address@hidden deffn
 
 @example
 define(`exch', `$2, $1')
@@ -1670,8 +1710,11 @@
 and for all the actual arguments.
 
 The number of actual arguments in a macro call is denoted by @code{$#}
-in the expansion text.  Thus, a macro to display the number of arguments
-given can be
+in the expansion text.
+
address@hidden Composite nargs (@dots{})
+Expands to a count of the number of arguments supplied.
address@hidden deffn
 
 @example
 define(`nargs', `$#')
@@ -1779,6 +1822,9 @@
 @result{}$$$ hello $$$
 @end example
 
address@hidden rescanning
address@hidden literal output
address@hidden output, literal
 If you want a macro to expand to something like @samp{$12}, the
 judicious use of nested quoting can put a safe character between the
 @code{$} and the next character, relying on the rescanning to remove the
@@ -1861,6 +1907,8 @@
 
 @cindex macros, how to rename
 @cindex renaming macros
address@hidden macros, displaying definitions
address@hidden definitions, displaying macro
 It is possible to rename an already defined macro.  To do this, you need
 the builtin @code{defn}:
 
@@ -1921,6 +1969,7 @@
 @result{}
 @end example
 
address@hidden rescanning
 However, it is important to remember that @code{m4} rescanning is purely
 textual.  If an unbalanced end-quote string occurs in a macro
 definition, the rescan will see that embedded quote as the termination
@@ -1943,6 +1992,8 @@
 @result{}AA'
 @end example
 
address@hidden builtins, special tokens
address@hidden tokens, builtin macro
 Using @code{defn} to generate special tokens for builtin macros outside
 of expected contexts can sometimes trigger warnings.  But most of the
 time, such tokens are silently converted to the empty string.
@@ -1963,6 +2014,8 @@
 @cindex macros, temporary redefinition of
 @cindex temporary redefinition of macros
 @cindex redefinition of macros, temporary
address@hidden definition stack
address@hidden stack, macro definition
 It is possible to redefine a macro temporarily, reverting to the
 previous definition at a later time.  This is done with the builtins
 @code{pushdef} and @code{popdef}:
@@ -2245,6 +2298,8 @@
 @section If-else construct, or multibranch
 
 @cindex comparing strings
address@hidden discarding input
address@hidden input, discarding
 The other conditional, @code{ifelse}, is much more powerful.  It can be
 used as a way to introduce a long comment, as an if-else construct, or
 as a multibranch, depending on the number of arguments supplied:
@@ -2317,6 +2372,8 @@
 @end example
 
 @cindex multibranches
address@hidden switch statement
address@hidden case statement
 However, @code{ifelse} can take more than four arguments.  If given more
 than four arguments, @code{ifelse} works like a @code{case} or @code{switch}
 statement in traditional programming languages.  If @var{string-1} and
@@ -2710,6 +2767,8 @@
 @node Debugging
 @chapter How to debug macros and input
 
address@hidden debugging macros
address@hidden macros, debugging
 When writing macros for @code{m4}, they often do not work as intended on
 the first try (as is the case with most programming languages).
 Fortunately, there is support for macro debugging in @code{m4}.
@@ -3044,6 +3103,8 @@
 @section Deleting whitespace in input
 
 @cindex deleting whitespace in input
address@hidden discarding input
address@hidden input, discarding
 The builtin @code{dnl} stands for ``Discard to Next Line'':
 
 @deffn Builtin dnl
@@ -3100,8 +3161,9 @@
 @node Changequote
 @section Changing the quote characters
 
address@hidden changing the quote delimiters
address@hidden quote delimiters, changing the
address@hidden changing quote delimiters
address@hidden quote delimiters, changing
address@hidden delimiters, changing
 The default quote delimiters can be changed with the builtin
 @code{changequote}:
 
@@ -3303,6 +3365,7 @@
 
 @cindex changing comment delimiters
 @cindex comment delimiters, changing
address@hidden delimiters, changing
 The default comment delimiters can be changed with the builtin
 macro @code{changecom}:
 
@@ -3447,6 +3510,9 @@
 
 @cindex lexical structure of words
 @cindex words, lexical structure of
address@hidden syntax, changing
address@hidden changing syntax
address@hidden regular expressions
 @quotation
 The macro @code{changeword} and all associated functionality is
 experimental.  It is only available if the @option{--enable-changeword}
@@ -3667,6 +3733,8 @@
 
 @cindex saving input
 @cindex input, saving
address@hidden deferring expansion
address@hidden expansion, deferring
 It is possible to `save' some text until the end of the normal input has
 been seen.  Text can be saved, to be read again by @code{m4} when the
 normal input has been exhausted.  This feature is normally used to
@@ -3877,6 +3945,7 @@
 @node Diversions
 @chapter Diverting and undiverting output
 
address@hidden deferring output
 Diversions are a way of temporarily saving output.  The output of
 @code{m4} can at any time be diverted to a temporary file, and be
 reinserted into the output stream, @dfn{undiverted}, again at a later
@@ -4024,6 +4093,8 @@
 @result{}Wrapped TEXT precedes diverted text.
 @end example
 
address@hidden discarding input
address@hidden input, discarding
 If output is diverted to a negative diversion, it is simply discarded.
 This can be used to suppress unwanted output.  A common example of
 unwanted output is the trailing newlines after macro definitions.  Here
@@ -4082,6 +4153,8 @@
 order given.  If no arguments are supplied, all diversions are
 undiverted, in numerical order.
 
address@hidden file inclusion
address@hidden inclusion, of files
 As a @acronym{GNU} extension, @var{diversions} may contain non-numeric
 strings, which are treated as the names of files to copy into the output
 without expansion.  A warning is issued if a file could not be opened.
@@ -4287,6 +4360,7 @@
 @node Index macro
 @section Searching for substrings
 
address@hidden substrings, locating
 Searching for substrings is done with @code{index}:
 
 @deffn Builtin index (@var{string}, @var{substring})
@@ -4316,14 +4390,17 @@
 @node Regexp
 @section Searching for regular expressions
 
address@hidden basic regular expressions
 @cindex regular expressions
address@hidden expressions, regular
 @cindex @acronym{GNU} extensions
 Searching for regular expressions is done with the builtin
 @code{regexp}:
 
 @deffn Builtin regexp (@var{string}, @var{regexp}, @ovar{replacement})
 Searches for @var{regexp} in @var{string}.  The syntax for regular
-expressions is the same as in @acronym{GNU} Emacs.
+expressions is the same as in @acronym{GNU} Emacs, which is similar to
+Basic Regular Expressions (@sc{BRE}) in @acronym{POSIX}.
 @ifnothtml
 @xref{Regexps, , Syntax of Regular Expressions, emacs, The GNU Emacs
 Manual}.
@@ -4333,6 +4410,8 @@
 @uref{http://www.gnu.org/@/software/@/emacs/@/manual/@/emacs.html#Regexps,
 Syntax of Regular Expressions} in the @acronym{GNU} Emacs Manual.
 @end ifhtml
+Support for Extended Regular Expressions (@sc{ERE}) is not available,
+but will be added in @acronym{GNU} M4 2.0.
 
 If @var{replacement} is omitted, @code{regexp} expands to the index of
 the first match of @var{regexp} in @var{string}.  If @var{regexp} does
@@ -4502,7 +4581,9 @@
 @node Patsubst
 @section Substituting text by regular expression
 
address@hidden basic regular expressions
 @cindex regular expressions
address@hidden expressions, regular
 @cindex pattern substitution
 @cindex substitution by regular expression
 @cindex @acronym{GNU} extensions
@@ -4973,10 +5054,7 @@
 @node Shell commands
 @chapter Macros for running shell commands
 
address@hidden executing UNIX commands
address@hidden running UNIX commands
 @cindex UNIX commands, running
address@hidden commands, running UNIX
 @cindex executing shell commands
 @cindex running shell commands
 @cindex shell commands, running
@@ -5032,7 +5110,6 @@
 @result{}Extensions are active
 @end example
 
address@hidden platform macro
 On UNIX systems, @acronym{GNU} @code{m4} will define @address@hidden
 by default, or @code{unix} when the @option{-G} option is specified.
 
@@ -5371,6 +5448,8 @@
 @node Location
 @section Printing current location
 
address@hidden location, input
address@hidden input location
 To make it possible to specify the location of an error, three
 utility builtins exist:
 
@@ -5785,7 +5864,7 @@
 is modeled after the C library function @code{printf} (@pxref{Format}).
 
 @item
-Searches and text substitution through regular expressions are
+Searches and text substitution through basic regular expressions are
 supported by the @code{regexp} (@pxref{Regexp}) and @code{patsubst}
 (@pxref{Patsubst}) builtins.
 
@@ -6035,7 +6114,6 @@
 @acronym{GNU} @code{m4} makes no attempt at prohibiting self-referential
 definitions like:
 
address@hidden ignore
 @example
 define(`x', `x')
 @result{}
@@ -6043,8 +6121,10 @@
 @result{}
 @end example
 
address@hidden rescanning
 There is nothing inherently wrong with defining @samp{x} to
-return @samp{x}.  The wrong thing is to expand @samp{x} unquoted.
+return @samp{x}.  The wrong thing is to expand @samp{x} unquoted,
+because that would cause an infinite rescan loop.
 In @code{m4}, one might use macros to hold strings, as we do for
 variables in other programming languages, further checking them with:
 
@@ -6054,11 +6134,11 @@
 @end example
 
 @noindent
-In cases like this one, an interdiction for a macro to hold its own
-name would be a useless limitation.  Of course, this leaves more rope
-for the @acronym{GNU} @code{m4} user to hang himself!  Rescanning hangs may be
-avoided through careful programming, a little like for endless loops
-in traditional programming languages.
+In cases like this one, an interdiction for a macro to hold its own name
+would be a useless limitation.  Of course, this leaves more rope for the
address@hidden @code{m4} user to hang himself!  Rescanning hangs may be
+avoided through careful programming, a little like for endless loops in
+traditional programming languages.
 @end itemize
 
 @node Answers
@@ -6173,6 +6253,8 @@
 @error{}m4trace: -3- shift(`4')
 @end example
 
address@hidden quadratic behavior, avoiding
address@hidden avoiding quadratic behavior
 Each successive iteration was adding more quoted @code{shift}
 invocations, and the entire list contents were passing through every
 iteration.  In general, when recursing, it is a good idea to make the
@@ -6413,27 +6495,24 @@
 @appendix Indices of concepts and macros
 
 @menu
-* Concept index::               Index for many concepts
 * Macro index::                 Index for all @code{m4} macros
+* Concept index::               Index for many concepts
 @end menu
 
address@hidden Concept index
address@hidden Index for many concepts
-
address@hidden cp
-
 @node Macro index
 @appendixsec Index for all @code{m4} macros
 
-References are exclusively to the places where a builtin is introduced
-the first time.
-
address@hidden
address@hidden 1
address@hidden iftex
+This index covers all @code{m4} builtins, as well as several useful
+composite macros.  References are exclusively to the places where a
+macro is introduced the first time.
 
 @printindex fn
 
address@hidden Concept index
address@hidden Index for many concepts
+
address@hidden cp
+
 @bye
 
 @c Local Variables: