Availability:built-in
If goal_expansion/2 wraps a goal as in the example below the system still reaches fixed-point as it prevents re-expanding the expanded term while recursing. It does re-enable expansion on the arguments of the expanded goal as illustrated in t2/1 in the example.57After discussion with Peter Ludemann and Paulo Moura on the forum.
:- meta_predicate run(0). may_not_fail(test(_)). may_not_fail(run(_)). goal_expansion(G, (G *-> true ; error(goal_failed(G),_))) :- may_not_fail(G). t1(X) :- test(X). t2(X) :- run(run(X)).
Is expanded into
t1(X) :- ( test(X) *-> true ; error(goal_failed(test(X)), _) ). t2(X) :- ( run((run(X)*->true;error(goal_failed(run(X)), _))) *-> true ; error(goal_failed(run(run(X))), _) ).