[Haskell-cafe] How to make callCC more dynamic

[Ertugrul Soeylemez]

bob zhang <bobzhang1988 at gmail.com> wrote:

>   I was curious that we could bring really continuations into haskell,
> the traditional callCC brings a lot of unnecessary type restrictions

That's where the misconception lies.  The type parameter /is/ necessary
for delimited continuations in Haskell.  By the way, I don't see how
these continuations would be in any way not "real" or how the type
parameter places any "restrictions", unless of course you want dynamic
typing.

The only operations I can imagine, which really restrict the type
parameter, are the operation of aborting the entire computation and
manipulating the result of it:

    abort    :: a -> ContT a m a
    mapContT :: (r -> r) -> ContT r m ()

You can have undelimited CPS without the type parameter, but then you
won't get any CPS effects.  As noted, you will just have an
IdentityT-like monad transformer, which can at best improve the
semantics of the underlying monad.


Greets,
Ertugrul


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