Re: Multimethod/multisub thought...

[Dan Sugalski]

At 10:02 AM -0800 1/24/03, Austin Hastings wrote:

--- Dan Sugalski <[EMAIL PROTECTED]> wrote:

 At 7:30 AM +0000 1/24/03, Piers Cawley wrote:
 >In my quest to eliminate as many explicit conditionals from my code
 as
 >possible, I found myself wondering if Perl 6's multidispatch
 mechanism
 >would allow one to write:

 Okay, I think I remembered the problem. Assume the following:

     list bar(int);   # bar takes an int, returns a list
     scalar bar(int); # bar takes an int, returns a scalar

 and also assume the following:

     xyzzy(scalar); # xyzzy takes a scalar
     xyzzy(list);   # xyzzy takes a list

 and then we make the call:

     xyzzy(bar(1));

 Which bar do we call? And which xyzzy?

In theory, if there's a return type expected, we could use that as the
final arbiter.

If not, but "if it looks like a scalar" ...

    xyzzy(bar 1); # Scalar
    xyzzy(bar(1)); # Scalar
    xyzzy(bar((1))); # List?
    xyzzy(bar(list(1))); #List
    xyzzy(bar(scalar(1))); # Scalar

There's also the fun of:

Dog bar(int);
Cat bar(int);

and

xyzzy(Dog);
xyzzy(Cat);

with the call of:

xyzzy(bar(1));

Just one of the many brain-benders that I'm glad Larry has to deal with, not me. (Though this may be one of the reasons A6 is taking so long...)
--
Dan

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