On Mon, 2008-10-13 at 19:51 +0100, Andrew Coppin wrote:
> {-# LANGUAGE FlexibleInstances #-}
>
> module Overload where
>
> class Silly s where
> go :: s
>
> instance Silly ([x] -> [x]) where
> go = reverse
>
> instance Silly (Int -> Int) where
> go = (+1)
>
>
>
>
>
> Don't even ask.
>
> Suffice it to say, you *can* make Haskell support arbitrary overloading
> of function names like C++ has, _if_ you abuse the type system violently
> enough. Please, won't somebody think of the children?!?
Flexible instances are extroardinarily useful:
instance Monad m => MonadState s (StateT s m)
instance MonadState t m => MonadState (s, t) (StateT s m)
is a useful and not entirely insane instance scheme.
But yeah, anyone who uses class Silly in real life should be banned from
coming within a 100 feet of any place where math, science, engineering,
or software development is carried out or taught.
I don't know if it's necessary for the good of the Children, but we need
to start thinking of the poor, defenseless computers as well...
jcc
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