Evaluation should stop early in some cases

[tsandall]

If a rule head does not contaIn vars, evaluation should stop after it finds the first proof for the body. Currently, evaluation/topdown continues to find all proofs. For instance:

OPA 0.4.0 (commit 4ea2b27, built at 2017-01-25T18:34:39Z)

Run 'help' to see a list of commands.

> p :- a = [1,2,3], a[_] > 0
> p
true
> trace
> p
Enter eq(data.repl.p, _)
| Eval eq(data.repl.p, _)
| Enter p = true
| | Eval eq(a, [1, 2, 3])
| | Eval gt(a[_], 0)
| | Exit p = true
| Redo p = true
| | Redo gt(1, 0)
| | Exit p = true
| Redo p = true
| | Redo gt(2, 0)
| | Exit p = true
| Exit eq(data.repl.p, _)
true

[tsandall]

Closing this due to inactivity.