gdb/doc/pretex.m4

   1 divert(-1)                              -*-Text-*-
   2 ` Copyright (c) 1991 Free Software Foundation, Inc.'
   3 ` This file defines and documents the M4 macros used '
   4 `      to preprocess some GNU manuals'
   5 ` $Id$'
   6
   7 I. INTRODUCTION
   8
   9 This collection of M4 macros is meant to help in pre-processing texinfo
  10 files to allow configuring them by hosts; for example, the reader of an
  11 as manual who only has access to a 386 may not really want to see crud about
  12 VAXen.
  13
  14 A preprocessor is used, rather than extending texinfo, because this
  15 way we can hack the conditionals in only one place; otherwise we would
  16 have to write TeX macros, update makeinfo, and update the Emacs
  17 info-formatting functions.
  18
  19 II. COMPATIBILITY
  20
  21 These macros should work with GNU m4 and System V m4; they do not work
  22 with Sun or Berkeley M4.
  23
  24 III. USAGE
  25
  26 A. M4 INVOCATION
  27 Assume this file is called "pretex.m4".  Then, to preprocess a
  28 document "mybook.texinfo" you might do something like the following:
  29
  30         m4 pretex.m4 none.m4 PARTIC.m4 mybook.texinfo >mybook-PARTIC.texinfo
  31
  32 ---where your path is set to find GNU or SysV "m4", and the other m4
  33 files mentioned are as follows:
  34
  35         none.m4: A file that defines, as 0, all the options you might
  36                 want to turn on using the conditionals defined below.
  37                 Unlike the C preprocessor, m4 does not default
  38                 undefined macros to 0.  For example, here is a "none.m4"
  39                 I have been using:
  40             _divert__(-1)
  41
  42             _define__(<_ALL_ARCH__>,<0>)
  43             _define__(<_INTERNALS__>,<0>)
  44
  45             _define__(<_AMD29K__>,<0>)
  46             _define__(<_I80386__>,<0>)
  47             _define__(<_I960__>,<0>)
  48             _define__(<_M680X0__>,<0>)
  49             _define__(<_SPARC__>,<0>)
  50             _define__(<_VAX__>,<0>)
  51
  52             _divert__<>
  53
  54         PARTIC.m4: A file that turns on whichever options you actually
  55                 want the manual configured for, in this particular
  56                 instance.  Its contents are similar to one or more of
  57                 the lines in "none.m4", but of course the second
  58                 argument to _define__ is <1> rather than <0>.
  59
  60                 This is also a convenient place to _define__ any macros
  61                 that you want to expand to different text for
  62                 different configurations---for example, the name of
  63                 the program being described.
  64
  65 Naturally, these are just suggested conventions; you could put your macro
  66 definitions in any files or combinations of files you like.
  67
  68 These macros use the characters < and > as m4 quotes; if you need
  69 these characters in your text, you will also want to use the macros
  70 _0__ and _1__ from this package---see the description of "Quote
  71 Handling" in the "Implementation" section below.
  72
  73 B. WHAT GOES IN THE PRE-TEXINFO SOURCE
  74
  75 For the most part, the text of your book.  In addition, you can
  76 have text that is included only conditionally, using the macros
  77 _if__ and _fi__ defined below.  They BOTH take an argument!  This is
  78 primarily meant for readability (so a human can more easily see what
  79 conditional end matches what conditional beginning), but the argument
  80 is actually used in the _fi__ as well as the _if__ implementation.
  81 You should always give a _fi__ the same argument as its matching
  82 _if__.  Other arguments may appear to work for a while, but are almost
  83 certain to produce the wrong output for some configurations.
  84
  85 For example, here is an excerpt from the very beginning of the
  86 documentation for GNU as, to name the info file appropriately for
  87 different configurations:
  88     _if__(_ALL_ARCH__)
  89     @setfilename as.info
  90     _fi__(_ALL_ARCH__)
  91     _if__(_M680X0__ && !_ALL_ARCH__)
  92     @setfilename as-m680x0.info
  93     _fi__(_M680X0__ && !_ALL_ARCH__)
  94     _if__(_AMD29K__ && !_ALL_ARCH__)
  95     @setfilename as-29k.info
  96     _fi__(_AMD29K__ && !_ALL_ARCH__)
  97
  98 Note that you can use Boolean expressions in the arguments; the
  99 expression language is that of the built-in m4 macro `eval', described
 100 in the m4 manual.
 101
 102 IV. IMPLEMENTATION
 103
 104 A.PRIMITIVE RENAMING
 105 First, we redefine m4's built-ins to avoid conflict with plain text.
 106 The naming convention used is that our macros all begin with a single
 107 underbar and end with two underbars.  The asymmetry is meant to avoid
 108 conflict with some other conventions (which we may want to document) that
 109 are intended to avoid conflict, like ANSI C predefined macros.
 110
 111 define(`_undefine__',defn(`undefine'))
 112 define(`_define__',defn(`define'))
 113 define(`_defn__',defn(`defn'))
 114 define(`_ppf__',`_define__(`_$1__',_defn__(`$1'))_undefine__(`$1')')
 115 _ppf__(`builtin')
 116 _ppf__(`changecom')
 117 _ppf__(`changequote')
 118 _ppf__(`decr')
 119 _ppf__(`define')
 120 _ppf__(`defn')
 121 _ppf__(`divert')
 122 _ppf__(`divnum')
 123 _ppf__(`dnl')
 124 _ppf__(`dumpdef')
 125 _ppf__(`errprint')
 126 _ppf__(`esyscmd')
 127 _ppf__(`eval')
 128 _ppf__(`format')
 129 _ppf__(`ifdef')
 130 _ppf__(`ifelse')
 131 _ppf__(`include')
 132 _ppf__(`incr')
 133 _ppf__(`index')
 134 _ppf__(`len')
 135 _ppf__(`m4exit')
 136 _ppf__(`m4wrap')
 137 _ppf__(`maketemp')
 138 _ppf__(`patsubst')
 139 _ppf__(`popdef')
 140 _ppf__(`pushdef')
 141 _ppf__(`regexp')
 142 _ppf__(`shift')
 143 _ppf__(`sinclude')
 144 _ppf__(`substr')
 145 _ppf__(`syscmd')
 146 _ppf__(`sysval')
 147 _ppf__(`traceoff')
 148 _ppf__(`traceon')
 149 _ppf__(`translit')
 150 _ppf__(`undefine')
 151 _ppf__(`undivert')
 152 _ppf__(`unix')
 153
 154 B. QUOTE HANDLING.
 155
 156 The characters used as quotes by M4, by default, are unfortunately
 157 quite likely to occur in ordinary text.  To avoid surprises, we will
 158 use the characters <> ---which are just as suggestive (more so to
 159 Francophones, perhaps) but a little less common in text (save for
 160 those poor Francophones.  You win some, you lose some).  Still, we
 161 expect also to have to set < and > occasionally in text; to do that,
 162 we define a macro to turn off quote handling (_0__) and a macro to
 163 turn it back on (_1__), according to our convention.
 164
 165         BEWARE: This seems to make < and > unusable as relational operations
 166                 in calls to the builtin "eval".  So far I've gotten
 167                 along without; but a better choice may be possible.
 168
 169 Note that we postponed this for a while, for convenience in discussing
 170 the issue and in the primitive renaming---not to mention in defining
 171 _0__ and _1__ themselves!  However, the quote redefinitions MUST
 172 precede the _if__ / _fi__ definitions, because M4 will expand the text
 173 as given---if we use the wrong quotes here, we will get the wrong
 174 quotes when we use the conditionals.
 175
 176 _define__(_0__,`_changequote__(\ 1,\ 2)')_define__(_1__,`_changequote__(<,>)')
 177 _1__
 178
 179 C. CONDITIONALS
 180
 181 We define two macros, _if__ and _fi__.  BOTH take arguments!  This is
 182 meant both to help the human reader match up a _fi__ with its
 183 corresponding _if__ and to aid in the implementation.  You may use the
 184 full expression syntax supported by M4 (see docn of `eval' builtin in
 185 the m4 manual).
 186
 187 The conditional macros are carefully defined to avoid introducing
 188 extra whitespace (i.e., blank lines or blank characters).  One side
 189 effect exists---
 190
 191         BEWARE: text following an `_if__' on the same line is
 192                 DISCARDED even if the condition is true; text
 193                 following a `_fi__' on the same line is also
 194                 always discarded.
 195
 196 The recommended convention is to always place _if__ and _fi__ on a
 197 line by themselves.  This will also aid the human reader.  TeX won't
 198 care about the line breaks; as for info, you may want to insert calls
 199 to `@refill' at the end of paragraphs containing conditionalized text,
 200 where you don't want line breaks separating unconditional from
 201 conditional text.  info formatting will then give you nice looking
 202 paragraphs in the info file.
 203
 204 Nesting: conditionals are designed to nest, in the following way:
 205 *nothing* is output between an outer pair of false conditionals, even
 206 if there are true conditionals inside.  A false conditional "defeats"
 207 all conditionals within it.  The counter _IF_FS__ is used to
 208 implement this; kindly avoid redefining it directly.
 209
 210 _define__(<_IF_FS__>,<0>)
 211
 212 NOTE: The definitions for our "pushf" and "popf" macros use eval
 213 rather than incr and decr, because GNU m4 (0.75) tries to call eval
 214 for us when we say "incr" or "decr"---but doesn't notice we've changed
 215 eval's name.
 216
 217 _define__(
 218         <_pushf__>,
 219         <_define__(<_IF_FS__>,
 220                 _eval__((_IF_FS__)+1))>)
 221 _define__(
 222         <_popf__>,
 223         <_ifelse__(0,_IF_FS__,
 224                         <<>_dnl__<>>,
 225                         <_define__(<_IF_FS__>,_eval__((_IF_FS__)-1))>)>)
 226
 227 _define__(
 228         <_if__>,
 229         <_ifelse__(1,_eval__( ($1) ),
 230                         <<>_dnl__<>>,
 231                         <_pushf__<>_divert__(-1)>)>)
 232 _define__(
 233         <_fi__>,
 234         <_ifelse__(1,_eval__( ($1) ),
 235                 <<>_dnl__<>>,
 236                 <_popf__<>_ifelse__(0,_IF_FS__,
 237                         <_divert__<>_dnl__<>>,<>)>)>)
 238
 239 D. CHAPTER/SECTION MACRO
 240 In a parametrized manual, the heading level may need to be calculated;
 241 for example, a manual that has a chapter on machine dependencies
 242 should be conditionally structured as follows:
 243         - IF the manual is configured for a SINGLE machine type,  use
 244 the chapter heading for that machine type, and run headings down
 245 from there (top level for a particular machine is chapter, then within
 246 that we have section, subsection etc);
 247         - ELSE, if MANY machine types are described in the chapter,
 248 use a generic chapter heading such as "@chapter Machine Dependencies",
 249 use "section" for the top level description of EACH machine, and run
 250 headings down from there (top level for a particular machine is
 251 section, then within that we have subsection, subsubsection etc).
 252
 253 The macro <_CHAPSEC__> is for this purpose: its argument is evaluated (so
 254 you can construct expressions to express choices such as above), then
 255 expands as follows:
 256    0: @chapter
 257    1: @section
 258    2: @subsection
 259    3: @subsubsection
 260  ...and so on.
 261
 262 _define__(<_CHAPSEC__>,<@_cs__(_eval__($1))>)
 263 _define__(<_cs__>,<_ifelse__(
 264                         0, $1, <chapter>,
 265                         1, $1, <section>,
 266                                 <sub<>_cs__(_eval__($1 - 1))>)>)
 267
 268 _divert__<>_dnl__<>