Author: audreyt
Date: Tue Sep 26 03:07:20 2006
New Revision: 12432
Modified:
doc/trunk/design/syn/S03.pod
Log:
* S03: Document that chained comparisons short-circuit,
and never evaluates its arguments more than once.
Modified: doc/trunk/design/syn/S03.pod
==============================================================================
--- doc/trunk/design/syn/S03.pod (original)
+++ doc/trunk/design/syn/S03.pod Tue Sep 26 03:07:20 2006
@@ -1151,7 +1151,7 @@
=head1 Chained comparisons
Perl 6 supports the natural extension to the comparison operators,
-allowing multiple operands.
+allowing multiple operands:
if 1 < $a < 100 { say "Good, you picked a number *between* 1 and 100." }
@@ -1159,6 +1159,14 @@
if 1 <= $roll1 == $roll2 <= 6 { print "Doubles!" }
+A chain of comparisons short-circuits if the first comparison fails:
+
+ 1 > 2 > die("this is never reached");
+
+Each argument in the chain will evaluate at most once:
+
+ 1 > $x++ > 2 # $x increments exactly once
+
Note: any operator beginning with C<< < >> must have whitespace
in front of it, or it will be interpreted as a hash subscript instead.
