def test_de_morgans_law(self):
t = '''
((not (and (a) (or (b) (not (c))))))
'''
actual = logical_expression.build(s_expression.parse(t))
actual = logical_expression.convert_to_nnf(actual)
# !(a && (b || !c)) -> !a || !(b || c) -> !a || (!b && c)
expected = node_type.LogicalOp(
op = node_type.OP_OR,
children = [
node_type.LogicalOp(
op = node_type.OP_NOT,
children = [
node_type.Atom(name='a')
]),
node_type.LogicalOp(
op = node_type.OP_AND,
children = [
node_type.LogicalOp(
op = node_type.OP_NOT,
children = [node_type.Atom(name='b')]),
node_type.Atom(name='c'),
])
])
self.assertEqual(expected, actual)
def test_neg_neg_is_pos(self):
t = '''
((not (not (a))))
'''
actual = logical_expression.build(s_expression.parse(t))
actual = logical_expression.convert_to_nnf(actual)
expected = node_type.Atom(name='a')
self.assertEqual(expected, actual)
def test_no_conversion_is_required(self):
t = '''
((or (a) (b)))
'''
actual = logical_expression.build(s_expression.parse(t))
actual = logical_expression.convert_to_nnf(actual)
expected = node_type.LogicalOp(
op = node_type.OP_OR,
children = [
node_type.Atom(name='a'),
node_type.Atom(name='b'),
])
self.assertEqual(expected, actual)