Author: larry
Date: Fri Feb 16 17:59:34 2007
New Revision: 13588
Modified:
doc/trunk/design/syn/S13.pod
Log:
Clarification of coercion declarations and semantics.
Modified: doc/trunk/design/syn/S13.pod
==============================================================================
--- doc/trunk/design/syn/S13.pod (original)
+++ doc/trunk/design/syn/S13.pod Fri Feb 16 17:59:34 2007
@@ -12,9 +12,9 @@
Maintainer: Larry Wall <[EMAIL PROTECTED]>
Date: 2 Nov 2004
- Last Modified: 17 Jan 2007
+ Last Modified: 16 Feb 2007
Number: 13
- Version: 6
+ Version: 7
=head1 Overview
@@ -143,15 +143,39 @@
=head1 Type Casting
-A class can use the C<< *infix:<as> >> submethod to declare that its objects
-can be cast to some other class:
+A class may define methods that allow it to respond as if it were a
+routine, array, or hash. The long forms are as follows:
- multi submethod *infix:<as> (IO) { $*OUT }
- multi submethod *infix:<as> (Int) { 1 }
- multi submethod *infix:<as> (Str) { "Hello" }
+ method postcircumfix:<( )> (|$capture) {...}
+ method postcircumfix:<[ ]> (|$capture) {...}
+ method postcircumfix:<{ }> (|$capture) {...}
-With the above declaration, C<$obj as "foo"> is equivalent to C<$obj as Str>,
-because the multi dispatch cares only about the class.
+Those are a bit unwieldy, so you may also use these short forms:
+
+ method &.( |$capture ) {...}
+ method @.[ *@@slices ] {...}
+ method %.{ *@@slices } {...}
+
+The actual sigil used doesn't matter as long as it's followed by a dot
+and the bracket pair containing the signature. (Note that the angle
+bracket subscripting form C<< .<a b c> >> automatically translates
+itself into a call to C< .{'a','b','c'} >, so defining methods for
+angles is basically useless.)
+
+The expected semantics of C<&.()> is that of a type coercion which may
+or may not create a new object. So if you say:
+
+ $fido = Dog.new($spot)
+
+it certainly creates a new C<Dog> object. But if you say:
+
+ $fido = Dog($spot)
+
+it might call C<Dog.new>, or it might pull a C<Dog> with Spot's
+identity from the dog cache, or it might do absolutely nothing if
+C<$spot> already knows how to be a C<Dog>. As a fallback, if no
+method responds to C<&.()>, the class will be asked to attempt to
+do C<Dog.new($spot)> instead.
=cut
