RE: Pattern Match Success Changes Types

[Mariano Suarez Alvarez]

On Tue, 12 May 1998, Koen Claessen wrote:

> Frank A. Christoph wrote:
> 
>  | With regard to merging Either instances, I agree with Simon that for most
>  | programs this will not buy you much, but there are two common kinds of
>  | programs where one could expect a significant effect on performance, just
>  | because of sheer scale.
> 
> It is not only Either instances who suffer from this. Consider the
> following definition of "map", which could be made by a naive user:
> 
>   map :: (a -> b) -> [a] -> [b]
>   map f (x:xs) = f x : map f xs
>   map f xs     = xs
> 
> Same problem here.

Where is the CSE in theis def of map? Why is it naive? (Hugs & ghc define
map on lists exactly like that.) Maybe I'm naive...

-- m

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