[Haskell-cafe] Phantoms

[Jules Bean]

Malcolm Wallace wrote:
> Andrew Coppin <andrewcoppin at btinternet.com> wrote:
> 
>>> instnace Show (Foo Int) ...
>>> instnace Show (Foo Double) ...
>>>   
>> ...WHY did I not think of this myself? o_O
> 
> Because it is not Haskell'98?  
> It requires {-# LANGUAGE OverlappingInstances #-}

No it doesn't?

It requires the much more semantically simple -XFlexibleInstances, as 
far as I know.

Overlapping would only be needed if there was also a polymorphic 
instance on Foo a?

Jules