Arrow Classes

[Raja R Harinath]

Alastair Reid <alastair@reid-hoffmann.net> writes:

>> I'm glad to hear there isn't a _serious_ cost (i.e. performance penalty)
>> for fine-grained hierarchies. 
>
> One cost which doesn't seem to have been mentioned is the programmer cost. 
>
> With the current Haskell Prelude, a matrix operation (say) might have type:
>
>   invert :: Num a => Matrix a -> Matrix a
>
> but, if we had one operation per class, the type might be:
>
>   invert :: (Add a, Subtract a, FromInteger a, Eq a, Multiply a) 
>          => Matrix a -> Matrix a
>
> More flexible but quite unwieldy.

IIRC, Clean essentially has this.  Though it's more like

  invert :: (+ a, - a, FromInteger a, = a, * a) => Matrix a -> Matrix a

(I may be wrong about the syntax and the specifics :-)

- Hari
-- 
Raja R Harinath ------------------------------ harinath@cs.umn.edu