more testsuite coverage for autoconf idioms

[Eric Blake]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

I have been working away on a series of patches to speed up recursive
macro handling (with a goal to make $@ handling linear instead of
quadratic).  That series is not ready yet, but in the process, I reached a
point where a series of incremental patches all would pass the m4
testsuite, but the final build failed miserably when trying to use it with
autoconf.  So I'm enhancing the m4 testsuite to trigger these cases,
making it easier to pinpoint where the regressions were added in my patch
series.  For the branch, the testsuite is contained entirely within the
m4.texinfo, hence adding some tests within @ignore blocks.  But for head,
I will move those tests to a more appropriate tests/*.at file.

- --
Don't work too hard, make some time for fun as well!

Eric Blake             address@hidden
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.5 (Cygwin)
Comment: Public key at home.comcast.net/~ericblake/eblake.gpg
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org

iD8DBQFHJSe184KuGfSFAYARAl4kAKDVk3v9ECmSA5ZRJPbW3E80SIOA6gCguqAM
0yJpFVCyxBsjTLxB1jVqRSY=
=e4Jx
-----END PGP SIGNATURE-----

>From 08d5b5e080e2ff7e6808cd32956031e03a467095 Mon Sep 17 00:00:00 2001
From: Eric Blake <address@hidden>
Date: Sun, 28 Oct 2007 16:51:28 -0600
Subject: [PATCH] More test coverage for autoconf usage patterns.

* doc/m4.texinfo (Inhibiting Invocation, Pseudo Arguments)
(Builtin): Add new undocumented tests.
(Shift): Document cond macro, and add new test.

Signed-off-by: Eric Blake <address@hidden>
---
 ChangeLog      |    7 ++++
 doc/m4.texinfo |  109 ++++++++++++++++++++++++++++++++++++++++++++++++++++----
 2 files changed, 109 insertions(+), 7 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 992ae22..737a6ec 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2007-10-28  Eric Blake  <address@hidden>
+
+       More test coverage for autoconf usage patterns.
+       * doc/m4.texinfo (Inhibiting Invocation, Pseudo Arguments)
+       (Builtin): Add new undocumented tests.
+       (Shift): Document cond macro, and add new test.
+
 2007-10-27  Eric Blake  <address@hidden>
 
        Document one use of changequote(`(',`)').
diff --git a/doc/m4.texinfo b/doc/m4.texinfo
index 677c859..d7c8140 100644
--- a/doc/m4.texinfo
+++ b/doc/m4.texinfo
@@ -1346,18 +1346,31 @@ empty string.
 
 @cindex 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:
+example would yield the string @samp{bcd}, exactly as if @code{m4}
+has been given @address@hidden(`abcde', `1', `3')}} as input:
 
 @example
 define(`x', `substr(ab')
 @result{}
-define(`y', `cde, `3', `2')')
+define(`y', `cde, `1', `3')')
 @result{}
 x`'y
address@hidden
address@hidden
 @end example
 
address@hidden
address@hidden Similar, but with argument references, to ensure good test
address@hidden coverage.
address@hidden
+define(`x1', `len(`$1'')
address@hidden
+define(`y1', ``$1')')
address@hidden
+x1(`01234567890123456789')y1(`98765432109876543210')
address@hidden
address@hidden example
address@hidden ignore
+
 Unquoted strings on either side of a quoted string are subject to
 being recognized as macro names.  In the following example, quoting the
 empty string allows for the second @code{macro} to be recognized as such:
@@ -1923,6 +1936,20 @@ foo)
 @result{}bar'
 @end example
 
address@hidden
address@hidden Not worth putting in the manual, but this example is needed for
address@hidden good test coverage of copying large strings across recursion
address@hidden levels.
+
address@hidden
+define(`echo', `$@')dnl
+len((echo(`01234567890123456789',
+          `01234567890123456789')echo(`98765432109876543210',
+                                      `98765432109876543210')))
address@hidden
address@hidden example
address@hidden ignore
+
 A @samp{$} sign in the expansion text, that is not followed by anything
 @code{m4} understands, is simply copied to the macro expansion, as any
 other text is.
@@ -2416,6 +2443,17 @@ builtin(`builtin',)
 @result{}
 @end example
 
address@hidden
address@hidden This example is not worth putting in the manual, but it is
address@hidden needed for full coverage.  Autoconf's m4_include relies heavily
address@hidden on this feature.
+
address@hidden
+builtin(`include', `foo')dnl
address@hidden
address@hidden example
address@hidden ignore
+
 @node Conditionals
 @chapter Conditionals, loops, and recursion
 
@@ -2475,7 +2513,7 @@ as a multibranch, depending on the number of arguments 
supplied:
 @deffnx Builtin ifelse (@var{string-1}, @var{string-2}, @var{equal}, @
   @ovar{not-equal})
 @deffnx Builtin ifelse (@var{string-1}, @var{string-2}, @var{equal-1}, @
-  @var{string-3}, @var{string-4}, @var{equal-2}, @dots{})
+  @var{string-3}, @var{string-4}, @var{equal-2}, @dots{}, @ovar{not-equal})
 Used with only one argument, the @code{ifelse} simply discards it and
 produces no output.
 
@@ -2619,8 +2657,65 @@ reverse(`foo', `bar', `gnats', `and gnus')
 
 While not a very interesting macro, it does show how simple loops can be
 made with @code{shift}, @code{ifelse} and recursion.  It also shows
-that @code{shift} is usually used with @samp{$@@}.  Sometimes, a
-recursive algorithm requires adding quotes to each element:
+that @code{shift} is usually used with @samp{$@@}.  Another example of
+this is an implementation of a short-circuiting conditional operator.
+
address@hidden short-circuiting conditional
address@hidden conditional, short-circuiting
address@hidden Composite cond (@var{test-1}, @var{string-1}, @var{equal-1}, @
+  @ovar{test-2}, @ovar{string-2}, @ovar{equal-2}, @dots{}, @ovar{not-equal})
+Similar to @code{ifelse}, where an equal comparison between the first
+two strings results in the third, otherwise the first three arguments
+are discarded and the process repeats.  The difference is that each
address@hidden<n>} is expanded only when it is encountered.  This means that
+every third argument to @code{cond} is normally given one more level of
+quoting than the corresponding argument to @code{ifelse}.
address@hidden deffn
+
+Here is the implementation of @code{cond}, along with a demonstration of
+how it can short-circuit the side effects in @code{side}.  Notice how
+all the unquoted side effects happen regardless of how many comparisons
+are made with @code{ifelse}, compared with only the relevant effects
+with @code{cond}.
+
address@hidden
+define(`cond',
+`ifelse(`$#', `1', `$1',
+        `ifelse($1, `$2', `$3',
+                `$0(shift(shift(shift($@@))))')')')dnl
+define(`side', `define(`counter', incr(counter))$1')dnl
+define(`example1',
+`define(`counter', `0')dnl
+ifelse(side(`$1'), `yes', `one comparison: ',
+       side(`$1'), `no', `two comparisons: ',
+       side(`$1'), `maybe', `three comparisons: ',
+       `side(`default answer: ')')counter')dnl
+define(`example2',
+`define(`counter', `0')dnl
+cond(`side(`$1')', `yes', `one comparison: ',
+     `side(`$1')', `no', `two comparisons: ',
+     `side(`$1')', `maybe', `three comparisons: ',
+     `side(`default answer: ')')counter')dnl
+example1(`yes')
address@hidden comparison: 3
+example1(`no')
address@hidden comparisons: 3
+example1(`maybe')
address@hidden comparisons: 3
+example1(`feeling rather indecisive today')
address@hidden answer: 4
+example2(`yes')
address@hidden comparison: 1
+example2(`no')
address@hidden comparisons: 2
+example2(`maybe')
address@hidden comparisons: 3
+example2(`feeling rather indecisive today')
address@hidden answer: 4
address@hidden example
+
+Sometimes, a recursive algorithm requires adding quotes to each element,
+or treating multiple arguments as a single element:
 
 @deffn Composite quote (@dots{})
 @deffnx Composite dquote (@dots{})
-- 
1.5.3.2