Re: lifting functions to tuples?

That only works for type constructors (or similar encapsulation functions), but not for any sort of a -> b functions, i.e. (+1).

How about this:

liftTup :: (forall a. a -> f a) -> (x, y) -> (f x, f y) liftTup f (x,y) = (f x, f y)

Or ghc can infer the type if you write it like this:

liftTup (f::forall a.a ->f a) (x::x,y::y) = (f x::f x, f y::f y)

or simply:

liftTup (f::forall a.a ->f a) (x,y) = (f x, f y)

It works too! (ghci -fglasgow-exts)

...

liftTup Just (1, 'c') (Just 1,Just 'c')

Duncan

_______________________________________________ Haskell mailing list Haskell@haskell.org http://www.haskell.org/mailman/listinfo/haskell