On Sun, Apr 29, 2007 at 07:03:32PM -0500, Antoine Latter wrote:
This looks like a good place to ask a question that's been bugging me for a bit:
I've had cases in my own code where I can't seem to create a type annotation for an "inner" declaration that the type-checker likes. Here's a toy example:
In the following code:
applyfunc :: (a -> b -> c) -> a -> b -> c applyfunc f x y = doit y where doit = f x
What type annotation can I successfully apply to the function "doit"?
There isn't one, plain and simple. However, if you allow GHC extensions, you can: {-# Language ScopedTypeVariables #-} applyfunc :: forall a b c . (a -> b -> c) -> a -> b -> c applyfunc f x y = doit y where doit :: b -> c doit = f x The 'forall' serves no other purpose than to deliberately break haskell 98 compatibility. Stefan