Author: larry
Date: Tue Sep 12 07:51:14 2006
New Revision: 11965
Modified:
doc/trunk/design/syn/S03.pod
Log:
Allow [=] and [+=].
Modified: doc/trunk/design/syn/S03.pod
==============================================================================
--- doc/trunk/design/syn/S03.pod (original)
+++ doc/trunk/design/syn/S03.pod Tue Sep 12 07:51:14 2006
@@ -12,9 +12,9 @@
Maintainer: Larry Wall <[EMAIL PROTECTED]>
Date: 8 Mar 2004
- Last Modified: 4 Sep 2006
+ Last Modified: 12 Sep 2006
Number: 3
- Version: 57
+ Version: 58
=head1 Changes to Perl 5 operators
@@ -802,8 +802,8 @@
=head2 Reduction operators
The final metaoperator in Perl 6 is the reduction operator. Any
-infix operator (except for non-associating operators and assignment
-operators) can be surrounded by square brackets in term position to
+infix operator (except for non-associating operators)
+can be surrounded by square brackets in term position to
create a list operator that reduces using that operation:
[+] 1, 2, 3; # 1 + 2 + 3 = 6
@@ -980,6 +980,26 @@
@args = (\%a,'foo','bar');
$x = [dehash] @args;
+Likewise, from the fact that list context flattens inner arrays and
+lists, it follows that a reduced assignment does no special syntactic
+dwimmery, and hence only scalar assigments are supported. Therefore
+
+ [=] $x, @y, $z, 0
+ [+=] $x, @y, $z, 1
+
+are equivalent to
+
+ $x = @y[0] = @y[1] = @y[2] ... @y[-1] = $z = 0
+ $x += @y[0] += @y[1] += @y[2] ... @y[-1] += $z += 1
+
+rather than
+
+ $x = @y = $z = 0;
+ $x += @y += $z += 1;
+
+(And, in fact, the latter are already easy to express anyway,
+and more obviously nonsensical.)
+
A reduce operator returns only a scalar result regardless of context.
(Even C<[,]> returns a single C<Capture> object which is then spliced
into the outer argument list.) To return all intermediate results,
