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RE: More on dispatching by function return type
On Tuesday, December 16, 2003 7:29 PM, Dan Sugalski
> I'm not sure CPS really has anything to do with it. CPS deals
> entirely with dispatching to and returning from (not that there's
> much difference) a function. Using the return type as part of the
> signature to determine which function to dispatch to seems orthogonal
> to how the dispatching actually happens.
I think that the idea is that we're presumably familiar with static
dispatch on argument types (both Java and C++ do this to resolve method
overloading). CPSing the program shifts the return type into argument
The type of read is
forall a. (Read a) => String -> a
where the dispatch occurs on the return type. The type of CPSed read
forall a r. (Read a) => String -> (a -> r) -> r
and the dispatch occurs on the static type of the second argument. If
you pass not as a continuation, you get a version of read specialized
for Bool, and if you pass (/ 2) you get a version of read specialized
for some Fractional instance.
But I agree that it's probably easier to just think of dispatch on
return type, since most programmers can't CPS-convert in their head.
(Another win for S-Expressions: you can CPS-convert in your sleep.)