Is there anything in particular you're trying to accomplish? It seems
like this is the type of thing you'd accomplish with typeclasses if
you had a less general problem than you've presented. For example,
mapShowTuple :: (Show a, Show b) => (a, b) -> (String, String)
mapShowTuple (x, y) = (show x, show y)
That said, it would be nice do be able to do something a little more
general, but still with a specific typeclass, like
mapNumOpTuple :: (Num a, Num b) => (Num c => c -> c) -> (a, b) -> (a, b)
mapNumOpTuple f (x, y) = (f x, f y)
(This unfortunately fails to typecheck; GHC chokes with "Illegal
polymorphic or qualified type". On the other hand, I'm still pretty
new to Haskell myself, so maybe someone else knows how to write this
correctly without doing complex type hackery.)
It would also be nice to be able to generalize over all typeclasses,
e.g. (pseudo-code here)
mapTypeclassOpTuple :: for all typeclasses C ((C a, C b) => (C c => c
-> c) -> (a, b) -> (a, b))
but I don't even know how that would fit into Haskell's syntax. I
suspect it's an idea that's been discussed, and I just don't know the
term for it.
Anyway, if you can make your problem more specific, it might be easier to solve.
--Grady
On 1/11/07, Marco Túlio Gontijo e Silva <[EMAIL PROTECTED]> wrote:
Hello,
is there a way to defined something as a map to use in tuples? I tried
this:
mapTuple f (a, b) = (f a, f b)
But the type inferred to it is not as generic as I wanted:
mapTuple :: (t -> t1) -> (t, t) -> (t1, t1)
Then I tried a different, but not much, implementation:
mapTuple' f g (a, b) = (f a, g b)
mapTuple f = mapTuple' f f
But the inferred type was the same.
Is there a way to define a function in which I can be able to do
something as this?
mapTuple show ("string", True)
--
malebria
Marco Túlio Gontijo e Silva
Correio (MSN): [EMAIL PROTECTED]
Jabber (GTalk): [EMAIL PROTECTED]
Telefone: 33346720
Celular: 98116720
Endereço:
Rua Paula Cândido, 257/201
Gutierrez 30430-260
Belo Horizonte/MG Brasil
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