nafc delays evaluation somehow until the args to the goal became ground. Is there some generic support for this delaying? I looked at the implementation but, well, didn't really get a clue. Maybe cgoal is the essence of it.

But in my actual use-case, I don't have a constraint but a relation (foo a b c) which requires that at least a and b, or c are ground. It would be nice if I could delay that until that is the case.

@tsdh: I think it’s in the IConstraintStep reification:

IRunnable
           (-runnable? [_]
             (every? #(ground-term? % s) args))))

https://github.com/clojure/core.logic/blob/master/src/main/clojure/clojure/core/logic.clj#L2711

@jballanc: That's probably it. I'll tinker around with that if I find some time.

Thanks

np