[m-dev.] Re: assertions (was: Assocative predicates)

[Zoltan Somogyi]

David Jeffery wrote:
> but I don't see how you can have an output constraint that is 
> different to an input constraint.

The idea is that (e.g.) you can call p/2 with the first argument
being of the form f(_) or g(_, _), but p/2 can succeed when the first
argument is of the form f(_) only; when called with a first argument
of the form g(_, _), it must fail.

Zoltan.