> -----Original Message----- > From: Larry Wall [mailto:[EMAIL PROTECTED] > > On Fri, Apr 23, 2004 at 01:15:51PM -0400, Austin Hastings wrote: > : A12 sez: > : > : If your delegation object happens to be an array: > : > : has @:handlers handles 'foo'; > : > : then something cool happens. <cool rays> In this case > : Perl 6 assumes that your array contains a list of potential > : handlers, and you just want to call the first one that > : succeeds. > : > : This is not clear, and I'm not liking it at the moment anyway. > It has the > : effect of saying: > : > : "If you HAS-A attribute that is an array, you cannot delegate > to it, but if > : you IS-A array, no worries." > : > : So Queue classes that start out: > : > : class Queue is Array {...} > : > : can get push/pop/splice whatever methods for free, but: > : > : class Queue is PersistentObject > : { > : has @:elements handles «push pop splice»; > : > : can not work (unless one of the things inside @:elements > happens to be an > : array). > > has $:elements handles «push pop splice»; > > can hold an array in that case.
This surprises me. case 1:s has $:obj handles 'a'; $:obj = new Foo; $self.a(); # Foo::a case 1:n has $:obj handles 'a'; $:obj = «new» (Foo, Bar, Baz); $self.a(); # one(Foo::a, Bar::a, Baz::a) case 1:a has $:obj handles 'a'; $:obj = «new» (Foo, Bar, Baz); $self.a(); # Array::a case a:n has @:obj handles 'a'; @:obj = «new» (Foo, Bar, Baz); $self.a(); # one(Foo::a, Bar::a, Baz::a) case a:a has @:obj handles 'a'; @:obj = «new» (Foo, Bar, Baz); $self.a(); # Array::a I guess I'm more strongly attached to the sigil than I realized. IMO, if you have $obj handles 'a'; and put an arrayref in $obj, then you get what's coming: iteration. But if you have @obj handles 'a'; then you know it's an array, or array subtype, and delegate array-things to it. So I prefer cases 1:s, 1:n, and a:a instead of 1:s, 1:a, and a:n. > : Also, it's not clear: > : > : "first one that succeeds" > : > : Does that mean "First one for which a matching method exists" or does it > : mean "First one for which a method exists that does not C<fail> > or return > : undef or some other badness"? > > The latter is the intent. Then array handling is doing some sort of .+method dispatch instead of "plain old dispatch", no? I think this should be made explicit. At first glance, I'd hate to lose C<return undef;> or C<return FALSE;> as an option just because than means "keep searching for handlers". Can you tell us why the initial spec calls for continuing search? =Austin
