From d0b3a5b8b20f282d6a3cefdd5845691cbed6a33a Mon Sep 17 00:00:00 2001
From: Alexandre Duret-Lutz <adl@gnu.org>
Date: Wed, 20 Nov 2002 22:33:15 +0000
Subject: [PATCH] * lib/Automake/Conditional.pm (strip): New function. *
 lib/Automake/ConditionalSet.pm (sub_conditions): Use it. Suggested by Raja R
 Harinath.

---
 ChangeLog                      |  4 ++++
 lib/Automake/Conditional.pm    | 22 ++++++++++++++++++++++
 lib/Automake/ConditionalSet.pm | 22 ++++++++++------------
 3 files changed, 36 insertions(+), 12 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 5a78c8a7..60fa609e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,9 @@
 2002-11-20  Alexandre Duret-Lutz  <adl@gnu.org>
 
+	* lib/Automake/Conditional.pm (strip): New function.
+	* lib/Automake/ConditionalSet.pm (sub_conditions): Use it.
+	Suggested by Raja R Harinath.
+
 	* automake.in (conditional_ambiguous_p, macro_define, rule_define,
 	require_variables): Use ->human instead of ->string.
 	* lib/Automake/Conditional.pm (string): Don't sort conditions, they
diff --git a/lib/Automake/Conditional.pm b/lib/Automake/Conditional.pm
index c2d6551f..df36938f 100644
--- a/lib/Automake/Conditional.pm
+++ b/lib/Automake/Conditional.pm
@@ -44,6 +44,10 @@ Automake::Conditional - record a conjunction of conditions
   # Likewise, but using a list of atomic conditional strings
   my $both2 = $cond->merge_conds ("COND3_FALSE");
 
+  # Strip from $both any subconditions which are in $other.
+  # This is the opposite of merge.
+  $cond = $both->strip ($other);
+
   # Return the list of conditions ("COND1_TRUE", "COND2_FALSE"):
   my @conds = $cond->conds;
 
@@ -228,6 +232,24 @@ sub merge_conds ($@)
   new Automake::Conditional $self->conds, @conds;
 }
 
+=item C<$newcond = $cond-E<gt>strip ($minuscond)>
+
+Return a new condition which has all the subconditions of C<$cond>
+except those of C<$minuscond>.  This is the opposite of C<merge>.
+
+=cut
+
+sub strip ($$)
+{
+  my ($self, $minus) = @_;
+  my @res;
+  foreach my $cond ($self->conds)
+    {
+      push @res, $cond unless $minus->has ($cond);
+    }
+  return new Automake::Conditional @res;
+}
+
 =item C<@list = $cond-E<gt>conds>
 
 Return the set of conditions defining C<$cond>, as strings.  Note that
diff --git a/lib/Automake/ConditionalSet.pm b/lib/Automake/ConditionalSet.pm
index 9ace53bf..b9fdb487 100644
--- a/lib/Automake/ConditionalSet.pm
+++ b/lib/Automake/ConditionalSet.pm
@@ -52,6 +52,13 @@ Automake::ConditionalSet - record a disjunction of conditions
   # that complements $set.
   my $inv = $set->invert;
 
+  # Multiply two ConditionalSets.
+  my $prod = $set1->multiply ($set2)
+
+  # Return the subconditions of a ConditionalSet with respect to
+  # a Conditional.  See the description for a real example.
+  my $subconds = $set->sub_conditions ($cond)
+
 =head1 DESCRIPTION
 
 A C<ConditionalSet> is a disjunction of atomic conditions.  In
@@ -712,7 +719,6 @@ C<ConditionalSet>.
 sub sub_conditions ($$)
 {
   my ($self, $subcond) = @_;
-  my @res;
 
   # Make $subcond blindingly apparent in the ConditionalSet.
   # For instance `$a->_multiply($b)' (from the POD example) is:
@@ -723,19 +729,11 @@ sub sub_conditions ($$)
   # 	 new Automake::Conditional ("FALSE"));
   my $prod = $self->_multiply ($subcond);
 
-  # Now, strip $subcond from the non-false Conditionals.
+  # Now, strip $subcond from the remaining (i.e., non-false) Conditionals.
+  my @res;
   foreach my $c ($prod->conds)
     {
-      if (! $c->false)
-	{
-	  my @rescond;
-	  foreach my $cc ($c->conds)
-	    {
-	      push @rescond, $cc
-		unless $subcond->has ($cc);
-	    }
-	  push @res, new Automake::Conditional @rescond;
-	}
+      push @res, $c->strip ($subcond) unless $c->false;
     }
   return new Automake::ConditionalSet @res;
 }
-- 
2.43.5