[Haskell-cafe] Re: The Proliferation of List-Like Types
ndmitchell at gmail.com
Wed Feb 20 11:31:48 EST 2008
> > full -> Maybe (item, full)
> Hrm, what exactly is the return data here? Is is the head and the
> tail if the list has >= 1 item, or Nothing otherwise? Or...?
Yes, its the projection onto another type:
 = Nothing
(x:xs) = Just (x, xs)
> What is the problem with MPTC in base?
MPTC is not a part of any Haskell standard. The rules surrounding MPTC
are not clear. People want to remove MPTC's/functional dependencies,
or modify them with associated types. Compilers such as nhc and yhc
can't implement them. Once they are in Haskell', with an associated
set of restrictions/overlap rules etc, then they can be freely used
with the base library.
More information about the Haskell-Cafe