rntz / ukanren Goto Github PK

That is expand until no change.
The reason for this is that when there is a chaining of variables say V 0 maps to V 1 and V 1 maps to t1. Later on when there is a unification of (V 0) with t2, the current implementation of expand only expands once to V 1 rather than t1, therefore instead of unifying t1 with t2, it discards the previous mapping of V 1 with t1 and replaces it with the new mapping of V 1 with t2 which is a bug.