Author: lwall
Date: 2009-10-09 02:16:10 +0200 (Fri, 09 Oct 2009)
New Revision: 28670
Modified:
docs/Perl6/Spec/S12-objects.pod
Log:
[S12] or there's this approach
Modified: docs/Perl6/Spec/S12-objects.pod
===================================================================
--- docs/Perl6/Spec/S12-objects.pod 2009-10-08 23:55:31 UTC (rev 28669)
+++ docs/Perl6/Spec/S12-objects.pod 2009-10-09 00:16:10 UTC (rev 28670)
@@ -1507,12 +1507,24 @@
Int:U Int:_ where !*.defined
Int:D Int:_ where *.defined
-A bare C<Int> may default differently in different circumstances.
-In variable declarations and in invocant declarations, C<:_> is
-assumed so that variables can convey undefinedness, whereas in a
-formal parameter that is not an invocant, C<:D> is assumed so that
-dispatch tends to fail to routines that are expecting defined values.
+In standard Perl 6, C<Int> is always assumed to mean C<Int:_>, but
+this default may be changed within a lexical scope by various pragmas.
+In particular,
+ use parameters :D;
+
+will cause non-invocant parameters to default to C<:D>, while
+
+ use invocant :D;
+
+will do the same for the invocant parameter. In such lexical
+scopes you may use the C<:_> form to get back to the standard behavior.
+Conjecturally,
+
+ use variables :D;
+
+would do the same for types used in variable declarations.
+
=head2 Multiple constraints
[Conjecture: This entire section is considered a guess at our
