Author: larry
Date: Sat Sep 6 21:22:00 2008
New Revision: 14580
Modified:
doc/trunk/design/syn/S03.pod
Log:
"where" as Junctional infix resembling "&", but with order guaranteed
Modified: doc/trunk/design/syn/S03.pod
==============================================================================
--- doc/trunk/design/syn/S03.pod (original)
+++ doc/trunk/design/syn/S03.pod Sat Sep 6 21:22:00 2008
@@ -12,9 +12,9 @@
Maintainer: Larry Wall <[EMAIL PROTECTED]>
Date: 8 Mar 2004
- Last Modified: 21 Jun 2008
+ Last Modified: 6 Jun 2008
Number: 3
- Version: 137
+ Version: 138
=head1 Overview
@@ -38,7 +38,7 @@
L Additive + - +| +^ ~| ~^ ?| ?^
L Replication x xx
X Concatenation ~
- X Junctive and &
+ X Junctive and & where
X Junctive or | ^
L Named unary sleep abs sin
N Nonchaining infix but does <=> leg cmp .. ..^ ^.. ^..^
@@ -947,6 +947,23 @@
$a & $b & $c ...
+=item *
+
+C<< infix:<where> >>, sequential junctional and operator
+
+ EXPR where EXPR where EXPR ...
+
+Can be used to construct ANDed patterns with the same semantics as
+C<< infix:<&> >>, but with left-to-right evaluation guaranteed, for use
+in guarded patterns:
+
+ $target ~~ MyType where .mytest1 where .mytest2
+
+This is useful when later tests might throw exceptions if earlier
+tests don't pass. This cannot be guaranteed by:
+
+ $target ~~ MyType & .mytest1 & .mytest2
+
=back
=head2 Junctive or (any) precedence
