[Haskell-cafe] Re: Dynamic typing of polymorphic functions
alfonso.acosta at gmail.com
Fri Dec 21 06:13:35 EST 2007
Thanks a lot for your answer, you turn out to end up solving every
problem I get stuck in :)
This bit was the essential part of it.
On Dec 20, 2007 11:47 AM, <oleg at okmij.org> wrote:
> -- it is important to give the signature to (,) below: we pack the cons
> -- function of the right type!
> cons :: forall a b. (Typeable a, Typeable b) =>
> Signal a -> Signal b -> Signal (a,b)
> cons (Signal sig1) (Signal sig2) =
> Signal (PrimSignal (Cons (toDyn ((,)::a->b->(a,b))) sig1 sig2))
> mapSnd :: (Typeable a, Typeable b) => Signal (b, a) -> Signal a
> mapSnd = mapSY snd
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