Fix associative-commutative relations and the use of term walk groundedness #40
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This comes along with a warning/clarification to the assoccomm relations. They have always walked the first argument, which, when used with the old `ground_order` would only account for improperly ordered terms when the second argument was fully ground (and the first wasn't). However, it would perform this check repeatedly, incurring a full-traversal cost on every iteration. This inefficiency has been rectified. The new "shallow" ground order should accomplish the same--and more--by reordering according to "groundness" only at next level of traversal. The assoccomm goals need to be updated so that they properly use this shallow ordering, though.
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ground_orderdoesn't really order terms in a way that avoids infinite recursion interm_walko(e.g. when called by thekanren.assoccommgoals). There should be a way to handle this—at least better than it currently does.This PR adds a new test,
test_eq_assoccomm_scaling, (an expected failure) that demonstrates how poorly theassoccommgoals perform.The test creates a decently sized term graph containing assoc-comm operators and another one that differs only at the top-level (i.e. one graph starts with an
addoperator and the other amul). This should be no problem, since the two cannot unify from the start due to the operator discrepancy. However, due to the way theassoccommgoals descend into all permutations, it currently takes too long to fail. The changes in this PR attempt to address this issue.test_eq_assoccomm_scalingto passThis PR replaces #27.