Re: Dispatch on context

Piers Cawley writes:
> So, I was wondering about how to do multidispatch based on the
> context in which something is called, which leads me to wonder if
> there's going to be a way of reifying calling context so I could
> write:
> 
>   method whatever($arg1, $arg2) 
>     { my multi whatever ($self, Scalar $context:
>                          $arg1, $arg2) { ... }
>       my multi whatever ($self, Array $context: 
>                          $arg1, $arg2) { ... }
>       whatever($_, want(), $arg1, $arg2) }

The way I see that happening is if we allow certain kinds of constants
in multi declarations.

    my multi whatever ($self, Class $context is derived(Scalar):
                       $arg1, $arg2) {...}

That'd be nice in a number of different ways.  Without this special
feature, an enabling level of indirection can be added with
parameterized types:

    my class ClassVal [Class $TYPE] {
        # Does nothing, and may even be optimized away
    }
    my multi whatever ($self, ClassVal[Scalar] $context:
                       $arg1, $arg2) {...}
    # ...

    whatever($_, ClassVal[want], $arg1, $arg2);
    #                          ^ does a : go here?

That doesn't handle inheritance correctly, but it can be made to,
provided proper introspection into $TYPE. 

Luke

• Dispatch on context by Piers Cawley
• Re: Dispatch on context by Luke Palmer