map and fmap

[Ashley Yakeley]

Cale Gibbard wrote:
> While we're at it, let's split MonadZero and MonadPlus --
> the decision to merge them was not well thought-out, and a lot of
> expressive power in type signatures is lost there.

This should be split into three classes, "MonadZero", "MonadPlus" and 
"MonadOr" owing to variations in instances of the current MonadPlus.

See:
   http://haskell.org/haskellwiki/MonadPlus
   http://haskell.org/haskellwiki/MonadPlus_reform_proposal

-- 
Ashley Yakeley
Seattle WA