Author: larry Date: Mon Oct 30 12:18:19 2006 New Revision: 13350 Modified: doc/trunk/design/syn/S03.pod
Log: 1st whack at applying dwimmy hypers to hashes. Modified: doc/trunk/design/syn/S03.pod ============================================================================== --- doc/trunk/design/syn/S03.pod (original) +++ doc/trunk/design/syn/S03.pod Mon Oct 30 12:18:19 2006 @@ -12,9 +12,9 @@ Maintainer: Larry Wall <[EMAIL PROTECTED]> Date: 8 Mar 2004 - Last Modified: 16 Oct 2006 + Last Modified: 30 Oct 2006 Number: 3 - Version: 72 + Version: 73 =head1 Changes to Perl 5 operators @@ -877,6 +877,34 @@ Beyond all that, "array of scalar" types are known at compile time not to need recursive hypers, so the operations can be vectorized aggressively. +Hypers may be applied to hashes as well as to lists. In this case +"dwimminess" says whether to ignore keys that do not exist +in the other hash, while "non-dwimminess" says to use all keys that are +in either hash. That is, + + %foo «+» %bar; + +gives you the intersection of the keys, while + + %foo »+« %bar; + +gives you the union of the keys. Asymmetrical hypers are also useful; +for instance, if you say: + + %outer »+» %inner; + +only the %inner keys that already exist in %outer will occur in the result. +Note, however, that you want + + %outer »+=« %inner; + +in order to pass accumulated statistics up a tree, assuming you want %outer +to have the union of keys. + +Unary hash hypers and binary hypers that have only one hash operand +will apply the hyper operator to just the values but return a new +hash value with the same set of keys as the original hash. + =head2 Reduction operators The fourth metaoperator in Perl 6 is the reduction operator. Any
