Dave Whipp wrote: > Perhaps I'm not fully groking the abstraction of the capture-object, but > it seems to me that there should be a slot in it for the method. For > dispatch, all three things are needed (invocant, method, args); so if > you're going to put two of them in one object, then maybe the third > thing belongs, too.
Hm, Perl 6 actually has two different ways of putting Capture to some
Code object... Following yesterday's P6AST draft I'll call them Call and
Apply respectively:
moose($obj: 1, 2); # this is Call
&moose.($obj: 1, 2); # this is Apply
elk(named => 'arg'); # this is Call
&elk.(named => 'arg'); # this is Apply
The difference is whether the Code is an object (Apply), or a "message"
name (Call). As the same argument list can be reused in both cases, it
seems the "method" part is better left out from the abstraction. That
allows:
my $cap = \("Hello", "World");
outs(*$cap); # Sub Call (may optimize to Apply if &outs is lexical)
$fh.say(*$cap); # Method Call
$output(*$cap); # Apply
This also makes multiple Captures easily composable:
say(*$cap, *$cap, *$cap); # "HelloWorldHelloWorldHelloWorld"
<P6C>
Of course, if we go all Smalltalkish, we can say that Apply is merely
sending the "postcircumfix:<( )>" message to the Code object, so that we
can treat _everything_ as a closure by defining:
# Below demonstrates a (IMHO) bad idea
sub postcircumfix:<( )> ($inv: \$cap) { say "Foo!" }
1.(); # "Foo!" - method call falling back to sub call
But this defeats common closure-based optimizations, and penalizes
functional programming style for no apparent gain, so I think the
method-full form and method-less form are still better separated in the AST.
</P6C>
Audrey
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