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http://git.sv.gnu.org/gitweb/?p=m4.git;a=commitdiff;h=bc9b4d7bf16c7571efe03debaf2c6f1d52a6a08d The branch, master has been updated via bc9b4d7bf16c7571efe03debaf2c6f1d52a6a08d (commit) from 1dd98ea10e065300cfa110b7305362c1f12ed00f (commit) Those revisions listed above that are new to this repository have not appeared on any other notification email; so we list those revisions in full, below. - Log ----------------------------------------------------------------- commit bc9b4d7bf16c7571efe03debaf2c6f1d52a6a08d Author: Eric Blake <[EMAIL PROTECTED]> Date: Sat May 3 13:31:14 2008 -0600 Document define_blind. * doc/m4.texinfo (Ifelse): Add a new composite macro. * THANKS: Update. Suggested by Mike R. Signed-off-by: Eric Blake <[EMAIL PROTECTED]> ----------------------------------------------------------------------- Summary of changes: ChangeLog | 7 ++++++ THANKS | 1 + doc/m4.texinfo | 57 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 65 insertions(+), 0 deletions(-) diff --git a/ChangeLog b/ChangeLog index 44df370..cd1f927 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,10 @@ +2008-05-03 Eric Blake <[EMAIL PROTECTED]> + + Document define_blind. + * doc/m4.texinfo (Ifelse): Add a new composite macro. + * THANKS: Update. + Suggested by Mike R. + 2008-05-01 Eric Blake <[EMAIL PROTECTED]> Avoid -Wshadow compiler warnings. diff --git a/THANKS b/THANKS index 4fd8db4..807bd1b 100644 --- a/THANKS +++ b/THANKS @@ -97,6 +97,7 @@ Mike Andrews [EMAIL PROTECTED] Mike Frysinger [EMAIL PROTECTED] Mike Howard [EMAIL PROTECTED] Mike Lijewski [EMAIL PROTECTED] +Mike R. [EMAIL PROTECTED] Mikhail Teterin [EMAIL PROTECTED] Nelson H. F. Beebe [EMAIL PROTECTED] Nick S. Kanakakorn [EMAIL PROTECTED] diff --git a/doc/m4.texinfo b/doc/m4.texinfo index c593a8d..75d7fc8 100644 --- a/doc/m4.texinfo +++ b/doc/m4.texinfo @@ -2996,6 +2996,63 @@ foo(`a', `b', `c') @result{}arguments:3 @end example +Since m4 is a macro language, it is even possible to write a macro that +makes defining blind macros easier: + [EMAIL PROTECTED] Composite define_blind (@var{name}, @ovar{value}) +Defines @var{name} as a blind macro, such that @var{name} will expand to [EMAIL PROTECTED] only when given explicit arguments. @var{value} should not +be the result of @code{defn} (@pxref{Defn}). This macro is only +recognized with parameters, and results in an empty string. [EMAIL PROTECTED] deffn + +Defining a macro to define another macro can be a bit tricky. We want +to use a literal @samp{$#} in the argument to the nested @code{define}. +However, if @samp{$} and @samp{#} are adjacent in the definition of [EMAIL PROTECTED], then it would be expanded as the number of +arguments to @code{define_blind} rather than the intended number of +arguments to @var{name}. The solution is to pass the difficult +characters through extra arguments to a helper macro [EMAIL PROTECTED] + +As for the limitation against using @code{defn}, there are two reasons. +If a macro was previously defined with @code{define_blind}, then it can +safely be renamed to a new blind macro using plain @code{define}; using [EMAIL PROTECTED] to rename it just adds another layer of [EMAIL PROTECTED], occupying memory and slowing down execution. And if a +macro is a builtin, then it would result in an attempt to define a macro +consisting of both text and a builtin token; this is not supported, and +the builtin token is flattened to an empty string. + +With that explanation, here's the definition, and some sample usage. +Notice that @code{define_blind} is itself a blind macro. + [EMAIL PROTECTED] +$ @kbd{m4 -d} +define(`define_blind', `ifelse(`$#', `0', ``$0'', +`_$0(`$1', `$2', `$'`#', `$'`0')')') [EMAIL PROTECTED] +define(`_define_blind', `define(`$1', +`ifelse(`$3', `0', ``$4'', `$2')')') [EMAIL PROTECTED] +define_blind [EMAIL PROTECTED] +define_blind(`foo', `arguments were $*') [EMAIL PROTECTED] +foo [EMAIL PROTECTED] +foo(`bar') [EMAIL PROTECTED] were bar +define(`blah', defn(`foo')) [EMAIL PROTECTED] +blah [EMAIL PROTECTED] +blah(`a', `b') [EMAIL PROTECTED] were a,b +defn(`blah') [EMAIL PROTECTED](`$#', `0', ``$0'', `arguments were $*') [EMAIL PROTECTED] example + @cindex multibranches @cindex switch statement @cindex case statement hooks/post-receive -- GNU M4 source repository
