[m-dev.] type class constraints

[Michael Day]

Hi,

type class constraints are at present only allowed upon type variables and
not concrete types. This only really affects type classes with multiple
parameters. For instance:

:- pred snort(T, T) <= is_funky(T, char).

This will be flagged as an error by the compiler, stating that such
constraints are not implemented. Will they be implemented and if so, when?
The lack of them appears to make multiple parameter type classes less
useful than they would otherwise be.

Michael



--------------------------------------------------------------------------
mercury-developers mailing list
Post messages to:       mercury-developers at cs.mu.oz.au
Administrative Queries: owner-mercury-developers at cs.mu.oz.au
Subscriptions:          mercury-developers-request at cs.mu.oz.au
--------------------------------------------------------------------------