[mercury-users] variable parameters in typeclass instances

[Ralph Becket]

> it does not appear to be possible to state the following:
> 
> % everything is an instance of the "pointless" typeclass:
> :- instance pointless(_).
> 
> % everything and int satisfy the "strange_relation" typeclass:
> :- instance strange_relation(int, T).
> 
> do these declarations have semantic problems that make them undesirable,
> or will they be supported in a future version of the compiler?

Er, why not just define polymorphic predicates for this sort of thing.
There's no need to use typeclasses here.

Ralph
--------------------------------------------------------------------------
mercury-users mailing list
post:  mercury-users at cs.mu.oz.au
administrative address: owner-mercury-users at cs.mu.oz.au
unsubscribe: Address: mercury-users-request at cs.mu.oz.au Message: unsubscribe
subscribe:   Address: mercury-users-request at cs.mu.oz.au Message: subscribe
--------------------------------------------------------------------------