On Sun, Oct 26, 2008 at 09:37:36PM -0400, Bob Rogers wrote:
> .sub 'main' :main
> foo('Hello')
> .end
> .sub foo :multi(String)
> .param pmc s
>
> say s
> .end
> [...]
> Which brings us to an interesting question: How can you decide what
> type to use for autoboxing before you've determined the actual sub
> you're going to call? And how can you find the sub without having the
> correct dispatch types up front?
According to t/pmc/multidispatch.t, :multi can specify 'string',
'int', and 'num' to match the native (non-PMC) types:
.sub p :multi(string)
.param string s
print s
.end
.sub p :multi(string, string)
.param string opt
.param string s
if opt != '-twice' goto no_twice
print s
print s
.return()
no_twice:
print s
.end
Based on this, I would expect foo('hello') to dispatch to
a sub via :multi(string) and not dispatch to :multi(String).
As far as I can tell, this hasn't been deprecated anywhere, and
is explicitly recognized in pdd27 (line 43):
=item - Dispatch considers both low-level (register) types
and high-level (PMC) types, as well as inherited and composed types.
Returning to chromatic's original post, "no applicable methods" is
actually what I would expect from the code given, since there are
no methods defined taking the 'string' or 'int' type as the first
argument. If there's a version that does work using String and
Integer :multi's, then perhaps that's the one with the bug.
It's also possible that I'm completely misinterpreting the
:multi semantics, but that's the way things have tended to work
up to now, and I haven't seen any documentation or messages
that contradict it.
Pm
