Re: O(n) patches and side effects

[Eric Blake]

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

According to Ralf Wildenhues on 8/22/2008 12:23 AM:
> Should foreach.m4 and m4sugar.m4 have comments to the end of
> "please keep macro names and semantics aligned with the other file"?

Yes, good idea.  I'm committing the patch below.

> Do you think we may need to put some measure in place to enforce this?

The testsuite already does much of this - the "recursion" test runs both
implementations (if you use m4 1.6) by messing around with __m4_version__
before calling m4_init.  My hope is that any one-sided API or semantic
changes would thus be caught.

> 
> Eric, you are an incredible m4 wizard.

Thanks for the compliment.  I've tried to give decent comments for all of
my hacks to make m4sugar fast, but readily admit that m4sugar is not the
best file for m4 beginners to go reading (lots of black magic in there).

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

Eric Blake             address@hidden
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.9 (Cygwin)
Comment: Public key at home.comcast.net/~ericblake/eblake.gpg
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org

iEYEARECAAYFAkiuwGUACgkQ84KuGfSFAYDd+QCgrtl2JLhqDJykKeUHoSUFuv8N
xmsAn2cNBKbFb5c6RYV1B3trce1oOk3v
=vj2/
-----END PGP SIGNATURE-----

>From ce818dc20b17a19312328acfcc8789b970542553 Mon Sep 17 00:00:00 2001
From: Eric Blake <address@hidden>
Date: Fri, 22 Aug 2008 07:26:33 -0600
Subject: [PATCH] Add reminder to keep dual implementations in sync.

* lib/m4sugar/m4sugar.m4: Add comments.
* lib/m4sugar/foreach.m4: Likewise.
Suggested by Ralf Wildenhues.

Signed-off-by: Eric Blake <address@hidden>
---
 ChangeLog              |    7 +++++++
 lib/m4sugar/foreach.m4 |    2 ++
 lib/m4sugar/m4sugar.m4 |   38 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 47 insertions(+), 0 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 6ddc9f5..6a642cd 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2008-08-22  Eric Blake  <address@hidden>
+
+       Add reminder to keep dual implementations in sync.
+       * lib/m4sugar/m4sugar.m4: Add comments.
+       * lib/m4sugar/foreach.m4: Likewise.
+       Suggested by Ralf Wildenhues.
+
 2008-08-22  Peter Eisentraut  <address@hidden>  (tiny change)
 
        Format warning and error messages to match GCS.
diff --git a/lib/m4sugar/foreach.m4 b/lib/m4sugar/foreach.m4
index c35d5d3..80f333d 100644
--- a/lib/m4sugar/foreach.m4
+++ b/lib/m4sugar/foreach.m4
@@ -76,6 +76,8 @@
 # are not future-proof.  Thus, this file is conditionally included as
 # part of m4_init(), only when it is detected that M4 probably has
 # quadratic behavior (ie. it lacks the macro __m4_version__).
+#
+# Please keep this file in sync with m4sugar.m4.
 
 # m4_foreach(VARIABLE, LIST, EXPRESSION)
 # --------------------------------------
diff --git a/lib/m4sugar/m4sugar.m4 b/lib/m4sugar/m4sugar.m4
index f2fde7a..6ee157c 100644
--- a/lib/m4sugar/m4sugar.m4
+++ b/lib/m4sugar/m4sugar.m4
@@ -363,6 +363,8 @@ m4_define([m4_ifndef],
 # }.
 # All the values are optional, and the macro is robust to active
 # symbols properly quoted.
+#
+# Please keep foreach.m4 in sync with any adjustments made here.
 m4_define([m4_case],
 [m4_if([$#], 0, [],
        [$#], 1, [],
@@ -386,6 +388,8 @@ m4_define([m4_case],
 #
 # All the values are optional, and the macro is robust to active symbols
 # properly quoted.
+#
+# Please keep foreach.m4 in sync with any adjustments made here.
 m4_define([m4_bmatch],
 [m4_if([$#], 0, [m4_fatal([$0: too few arguments: $#])],
        [$#], 1, [m4_fatal([$0: too few arguments: $#: $1])],
@@ -446,6 +450,8 @@ m4_define([_m4_cdr],
 #
 # In the common case of $1 with no backslash, only one m4_index expansion
 # occurs, and m4_eval is avoided altogether.
+#
+# Please keep foreach.m4 in sync with any adjustments made here.
 m4_define([m4_cond],
 [m4_if([$#], [0], [m4_fatal([$0: cannot be called without arguments])],
        [$#], [1], [$1],
@@ -481,6 +487,8 @@ m4_define([_m4_cond],
 #
 # Recall that m4_shift3 always results in an argument.  Hence, we need
 # to distinguish between a final deletion vs. ending recursion.
+#
+# Please keep foreach.m4 in sync with any adjustments made here.
 m4_define([m4_bpatsubsts],
 [m4_if([$#], 0, [m4_fatal([$0: too few arguments: $#])],
        [$#], 1, [m4_fatal([$0: too few arguments: $#: $1])],
@@ -600,6 +608,8 @@ m4_ifdef([__m4_version__], [],
 #         [_m4_shiftn(m4_decr([$1]), m4_shift(m4_shift($@)))])
 # but with the final `m4_shift(m4_shift($@)))' shared between the two
 # paths.  The first leg uses a no-op m4_shift(,$@) to balance out the ().
+#
+# Please keep foreach.m4 in sync with any adjustments made here.
 m4_define([m4_shiftn],
 [m4_assert(0 < $1 && $1 < $#)_$0($@)])
 
@@ -708,6 +718,8 @@ m4_define([m4_count], [$#])
 # useful for making your macros more structured and readable by dropping
 # unnecessary dnl's and have the macros indented properly.  No concatenation
 # occurs after a STRING; use m4_unquote(m4_join(,STRING)) for that.
+#
+# Please keep foreach.m4 in sync with any adjustments made here.
 m4_define([m4_do],
 [m4_if([$#], 0, [],
        [$#], 1, [$1[]],
@@ -723,6 +735,8 @@ m4_define([m4_dquote],  address@hidden)
 # m4_dquote_elt(ARGS)
 # -------------------
 # Return ARGS as an unquoted list of double-quoted arguments.
+#
+# Please keep foreach.m4 in sync with any adjustments made here.
 m4_define([m4_dquote_elt],
 [m4_if([$#], [0], [],
        [$#], [1], [[[$1]]],
@@ -820,6 +834,8 @@ m4_define([_m4_quote],
 # m4_reverse(ARGS)
 # ----------------
 # Output ARGS in reverse order.
+#
+# Please keep foreach.m4 in sync with any adjustments made here.
 m4_define([m4_reverse],
 [m4_if([$#], [0], [], [$#], [1], [[$1]],
        [$0(m4_shift($@)), [$1]])])
@@ -984,6 +1000,8 @@ m4_define([_m4_for],
 # [] and use m4_car/m4_cdr for recursion, we instead unbox the list (which
 # requires swapping the argument order in the helper), insert an ignored
 # third argument, and use m4_shift3 to detect when recursion is complete.
+#
+# Please keep foreach.m4 in sync with any adjustments made here.
 m4_define([m4_foreach],
 [m4_if([$2], [], [],
        [m4_pushdef([$1])_$0([$1], [$3], [], $2)m4_popdef([$1])])])
@@ -1023,6 +1041,8 @@ m4_define([m4_foreach_w],
 # _m4_map.  For m4_map, an empty list behaves like an empty sublist
 # and gets ignored; for m4_mapall, we must special-case the empty
 # list.
+#
+# Please keep foreach.m4 in sync with any adjustments made here.
 m4_define([m4_map],
 [_m4_map([_m4_apply([$1]], [], $2)])
 
@@ -1066,6 +1086,8 @@ m4_define([_m4_mapall_sep],
 # then appends `,', the current SUBLIST and the closing `)', then
 # recurses to the next SUBLIST.  IGNORED is an aid to ending recursion
 # efficiently.
+#
+# Please keep foreach.m4 in sync with any adjustments made here.
 m4_define([_m4_map],
 [m4_if([$#], [2], [],
        [$1, [$3])$0([$1], m4_shift2($@))])])
@@ -1074,6 +1096,8 @@ m4_define([_m4_map],
 # --------------------------------
 # Expand EXPRESSION([ARG]) for each argument.  More efficient than
 # m4_foreach([var], [ARG...], [EXPRESSION(m4_defn([var]))])
+#
+# Please keep foreach.m4 in sync with any adjustments made here.
 m4_define([m4_transform],
 [m4_if([$#], [0], [m4_fatal([$0: too few arguments: $#])],
        [$#], [1], [],
@@ -1093,6 +1117,8 @@ m4_define([m4_transform],
 #   => (a,b)
 #   => (c,d)
 #   => (e)
+#
+# Please keep foreach.m4 in sync with any adjustments made here.
 m4_define([m4_transform_pair],
 [m4_if([$#], [0], [m4_fatal([$0: too few arguments: $#])],
        [$#], [1], [m4_fatal([$0: too few arguments: $#: $1])],
@@ -1952,6 +1978,8 @@ m4_define([m4_normalize],
 # elements, and outputs them following a separator.  The final trick to
 # note is that we decide between recursing with $0 or _$0 based on the
 # nested m4_if ending with `_'.
+#
+# Please keep foreach.m4 in sync with any adjustments made here.
 m4_define([m4_join],
 [m4_if([$#], [1], [],
        [$#], [2], [[$2]],
@@ -1964,6 +1992,8 @@ m4_define([_m4_join],
 # ------------------------------
 # Produce ARG1SEPARG2...SEPARGn.  An empty ARG results in back-to-back SEP.
 # No expansion is performed on SEP or ARGs.
+#
+# Please keep foreach.m4 in sync with any adjustments made here.
 m4_define([m4_joinall], [[$2]_$0([$1], m4_shift($@))])
 m4_define([_m4_joinall],
 [m4_if([$#], [2], [], [[$1$3]$0([$1], m4_shift2($@))])])
@@ -2240,6 +2270,8 @@ m4_define([m4_cmp],
 # which list is trimmed by one element; this is more efficient than
 # calling m4_cdr on both lists from a single macro.  Guarantee exactly
 # one expansion of both lists' side effects.
+#
+# Please keep foreach.m4 in sync with any adjustments made here.
 m4_define([m4_list_cmp],
 [_$0_raw(m4_dquote($1), m4_dquote($2))])
 
@@ -2265,6 +2297,8 @@ m4_define([_m4_list_cmp_2],
 # M4 1.4.x doesn't provide ?:.  Hence this huge m4_eval.  Avoid m4_eval
 # if both arguments are identical, but be aware of m4_max(0xa, 10) (hence
 # the use of <=, not just <, in the second multiply).
+#
+# Please keep foreach.m4 in sync with any adjustments made here.
 m4_define([m4_max],
 [m4_if([$#], [0], [m4_fatal([too few arguments to $0])],
        [$#], [1], [m4_eval([$1])],
@@ -2289,6 +2323,8 @@ m4_define([_m4_min],
 # ---------------------------------
 # Common recursion code for m4_max and m4_min.  METHOD must be _m4_max
 # or _m4_min, and there must be at least two arguments to combine.
+#
+# Please keep foreach.m4 in sync with any adjustments made here.
 m4_define([_m4_minmax],
 [m4_if([$#], [3], [$1([$2], [$3])],
        [$0([$1], $1([$2], [$3]), m4_shift3($@))])])
@@ -2448,6 +2484,8 @@ m4_define([m4_set_add],
 # not pruned.  The recursion helpers ignore their second argument, so
 # that we can use the faster m4_shift2 and 2 arguments, rather than
 # _m4_shift2 and one argument, as the signal to end recursion.
+#
+# Please keep foreach.m4 in sync with any adjustments made here.
 m4_define([m4_set_add_all],
 [m4_define([_m4_set_size($1)], m4_eval(m4_set_size([$1])
   + m4_len(m4_ifdef([_m4_set_cleanup($1)], [_$0_check], [_$0])([$1], $@))))])
-- 
1.6.0