Arrow Classes

[Graham Klyne]

At 10:58 12/07/03 +0100, Alastair Reid wrote:
>we could have 'context synonyms' like:
>
>   class Num a => (Add a, Subtract a, FromInteger a, Eq a, Multiply a, ...)
>
>Adding context synonyms would make it possible to write types concisely when
>using fine-grained class hierarchies and would also be useful with extensions
>like Hugs' T-REX or implicit parameters.

I must be missing something... isn't the effect achieved by:

   class (Add a, Subtract a, FromInteger a, Eq a, Multiply a, ...) => Num a

?

I guess it would be nice if declaring an instance of Num could specify the 
methods for Add, Subtract, etc...), but that seems a small thing, and I'm 
not sure it wouldn't introduce other problems.

#g


-------------------
Graham Klyne
<GK@NineByNine.org>
PGP: 0FAA 69FF C083 000B A2E9  A131 01B9 1C7A DBCA CB5E