On Sun Oct 31 16:38:58 2010, util wrote:
> On Rakudo Star 2010-10, this code works as expected, outputting "42\n"
> :
> multi sub Bar ( ) { return 42 };
> say Bar();
> This code should give the same output (and *does* on Pugs):
> multi sub Bar ( ) { return 42 };
> multi sub Bar (:$baz!) { return $baz };
> say Bar();
> Instead, Rakudo dies on this error:
> No applicable candidates found to dispatch to for 'Bar'. Available
> candidates are:
> :()
> :(Any :baz($baz)!)
Fixed:
17:07 < [Coke]> rakudo: multi sub Bar ( ) { return 42 }; multi sub Bar
(:$baz!)
{ return $baz }; say Bar();
17:07 <+p6eval> rakudo 33f1cf: OUTPUT«42»
Closable with tests.
> IMHO, required named parameters should default to being part of the
> longname.
> In any case, the current behavior looks like a bug.
>
> From http://irclog.perlgeek.de/perl6/2010-10-31#i_2956591
> < Util> perl6: say Bar(); multi sub Bar ( ) { return 42 };
> <+p6eval> pugs, rakudo 5f5bae: OUTPUT<<42NL>>
> < Util> perl6: say Bar(); multi sub Bar ( ) { return 42 }; multi
> sub Bar (:$baz!) { return $baz };
> <+p6eval> rakudo 5f5bae: OUTPUT<<No applicable candidates found to
> dispatch to for 'Bar'. Available candidates
> are:NL:()NL:(Any :baz($baz)!)NLNL in main program body
> at line 22:/tmp/UGNiomLxSCNL>>
> <+p6eval> ..pugs: OUTPUT<<42NL>>
> < Util> In Rakudo, why is the second declaration interfering?
> < masak> looks like a bug to me.
> < masak> ...possibly reported already.
> < sorear> Perl 6.0 is not required to support multiple dispatch
> with named parameters
> < masak> but I thought Rakudo did.
> < jnthn> No
> < jnthn> Well, it doesn't consider them other than as constraints.
> < jnthn> e.g. if one is required it's a constraint.
> < Util> sorear: it is more than just a named parm; it is a
> *required* named parm.
> Shouldn't that make it part of the dispatch?
> < masak> apparently, it's difficult to do that in practice.
> < jnthn> Rakudo already considered required named params as
> constraints.
> < jnthn> Otherwise a bunch of our trait_mods would never work.
> < jnthn> It even has an optimization for the
> single-required-named-param case. :-)
> < jnthn> Util: Can you file a ticket?
> < jnthn> That looks like a bug to me. :S
> < Util> Will file rakudobug. Thanks, all!
> < jnthn> Util++
> < jnthn> But it turns out to be a silly thinko. :-)
> < jnthn> Somewhere in that little file, perl6multisub.pmc :-)
> < jnthn> masak: There's another one in RT that I think is distinct
> from this but may end up related in the end.
> < masak> jnthn: ok. I didn't find anything about required nameds.
> < jnthn> masak: I think it was about an argless candidate.
> < jnthn> Or at least, that's the common dominator between these
> two.
>
--
Will "Coke" Coleda
