def primitives():
kb = Knowledge()
prover = Prover(kb)
def testpred(literal, prover):
if literal[0].is_const():
yield clause(literal)
else:
yield clause(lit(literal.pred, [const('foo')]))
yield clause(lit(literal.pred, [const('bar')]))
yield clause(lit(literal.pred, [const('baz')]))
kb.add_primitive(pred('testpred',1), testpred)
l1 = lit(pred('y', 1), [var('X')])
l2 = lit(pred('testpred', 1), [var('X')])
c1 = clause(l1, [l2])
kb.assert_clause(c1)
query = lit(pred('y',1),[var('X')])
answer = prover.ask(query)
assert set(answer) == set([lit(pred('y',1), [const('foo')]), lit(pred('y',1), [const('bar')]), lit(pred('y',1), [const('baz')])])
query = lit(pred('y',2), [const('twelve'), var('X')])
answer = prover.ask(query)
assert not set(answer)
kb.assert_clause(clause(lit(pred('testpred', 1), [const('quux')]), []))
query = lit(pred('y',1),[var('X')])
answer = prover.ask(query)
assert set(answer) == set([lit(pred('y',1), [const('foo')]), lit(pred('y',1), [const('bar')]), lit(pred('y',1), [const('baz')]), lit(pred('y',1), [const('quux')])])
query = lit(pred('y',2), [const('twelve'), var('X')])
answer = prover.ask(query)
assert not set(answer)
