> 1.
> Haskell-98 description
> - is it ready to print as the final, accepted and approved document?
Design frozen: but I'm working right now on the actual final document.
> class Num' a where add,sub :: a -> a -> a
> neg :: a -> a
> sub x y = add x (neg y)
>
> What might be the cost overhead (depending on implementation!),
> if we move sub to separate polymorphic function:
>
> sub :: Num' a => a -> a -> a
> sub x y = add x (neg y)
In GHC the efficiency differences either way are pretty slight.
I think.
> Module export:
> if a module N has to export only a couple of instances for the
> constructor defined in M, how does it say that nothing else is for
> export?
> Thus, in the following example, one has to hide
> localThing1, localThing2:
> module M ( C(..), ... )
> where
> data C a = ...
> -------------------
> module N ( ?? )
> where
> import M (C(..))
> instance ...=> I1 (C a) where c x = localThing1 x
> instance ...=> I2 (C a) ...
>
> localThing1 = ...
> localThing2 = ...
>
>
> Probably, module N (C(..)) will do. Have we really to re-export C ?
So the idea is *all* N does is to define instances? The H98 report
Section 5.4 says that if you import a module you get all the instances
in it. Period. So N doesn't need to export anything:
module N() where
import M
instance ...
instance ...
module Client where
import N -- You get N's instances and nothing else
Simon
