Author: larry
Date: Fri May 19 11:13:09 2006
New Revision: 9302
Modified:
doc/trunk/design/syn/S03.pod
Log:
Refined hyperops a bit.
Modified: doc/trunk/design/syn/S03.pod
==============================================================================
--- doc/trunk/design/syn/S03.pod (original)
+++ doc/trunk/design/syn/S03.pod Fri May 19 11:13:09 2006
@@ -12,9 +12,9 @@
Maintainer: Larry Wall <[EMAIL PROTECTED]>
Date: 8 Mar 2004
- Last Modified: 18 May 2006
+ Last Modified: 19 May 2006
Number: 3
- Version: 34
+ Version: 35
=head1 Changes to existing operators
@@ -326,7 +326,7 @@
(1,1,2,3,5) »+« (1,2,3,5,8); # (2,3,5,8,13)
-If one argument is insufficiently dimensioned, Perl "upgrades" it:
+If either argument is insufficiently dimensioned, Perl "upgrades" it:
(3,8,2,9,3,8) >>-<< 1; # (2,7,1,8,2,7)
@@ -354,11 +354,26 @@
[[1, 2], 3] »+« [4, [5, 6]] # [[1,2] »+« 4, 3 »+« [5, 6]]
# == [[5, 6], [8, 9]]
-You are not allowed to define your own hyper operators, because they are
-supposed to have consistent semantics derivable entirely from the modified
-scalar operator. If you're looking for a mathematical vector product, this
-isn't where you'll find it. A hyperoperator is one of the ways that you
-can promise to the optimizer that your code is parallelizable.
+More generally, hyper operators work recursively for any object
+matching the C<Each> role even if the object itself doesn't support
+the operator in question:
+
+ Bag(3,8,[2,Seq(9,3]],8) >>-<< 1; # Bag(2,7,[1,Seq(8,2)],7)
+ Bag(3,8,[2,Seq(9,3)],8) >>-<< (1,1,1,1); # Bag(2,7,[1,Seq(8,2)],7)
+ Bag(3,8,[2,Seq(9,3)],8) >>-<< (1,1,2,1); # Bag(2,7,[2,Seq(9,3)],7)
+
+In particular, tree node types with C<Each> semantics enable visitation:
+
+ $tree.».foo; # short for $tree.each: { .foo }
+
+You are not allowed to define your own hyper operators, because they
+are supposed to have consistent semantics derivable entirely from
+the modified scalar operator. If you're looking for a mathematical
+vector product, this isn't where you'll find it. A hyperoperator
+is one of the ways that you can promise to the optimizer that your
+code is parallelizable. (The tree visitation above is allowed to
+have side effects, but it is erroneous for the meaning of those side
+effects to depend on the order of visitation.)
=head1 Reduction operators
