def test_rule_notself(self):
ctx = Backward()
ctx.evaluate("""
!A => A
""")
ans = ctx.evaluate("A")
self.assertEqual(ans, [True])
def test_and(self):
ctx = Backward()
ans = ctx.evaluate("= a b c")
ans = ctx.evaluate("a & b & c")
self.assertEqual(ans, [True])
ans = ctx.evaluate("a & !b & c")
self.assertEqual(ans, [False])
ans = ctx.evaluate("a & !(!b & !c)")
self.assertEqual(ans, [True])
def test_rule(self):
ctx = Backward()
ans = ctx.evaluate("a => b")
ans = ctx.evaluate("b => c")
ans = ctx.evaluate("= a")
ans = ctx.evaluate("a b c")
self.assertEqual(ans, [True, True, True])
ans = ctx.evaluate("a => d & e & f")
ans = ctx.evaluate("d e f")
self.assertEqual(ans, [True, True, True])
def test_xor(self):
ctx = Backward()
ans = ctx.evaluate("= a c")
ans = ctx.evaluate("a ^ c")
self.assertEqual(ans, [False])
ans = ctx.evaluate("!a ^ c")
self.assertEqual(ans, [True])
ans = ctx.evaluate("a ^ !c")
self.assertEqual(ans, [True])
ans = ctx.evaluate("a ^ b")
self.assertEqual(ans, [True])
def test_or(self):
ctx = Backward()
ans = ctx.evaluate("= a c")
ans = ctx.evaluate("!a | c")
self.assertEqual(ans, [True])
ans = ctx.evaluate("a | !c")
self.assertEqual(ans, [True])
ans = ctx.evaluate("b | c")
self.assertEqual(ans, [True])
ans = ctx.evaluate("!a | !c")
self.assertEqual(ans, [False])
def test_atom(self):
ctx = Backward()
ans = ctx.evaluate("a")
self.assertEqual(ans, [False])
ans = ctx.evaluate("= a c")
ans = ctx.evaluate("a b c")
self.assertEqual(ans, [True, False, True])
ans = ctx.evaluate("=")
ans = ctx.evaluate("a b c")
self.assertEqual(ans, [False, False, False])
ans = ctx.evaluate("!a")
self.assertEqual(ans, [True])
def test_rule_and(self):
ctx = Backward()
ans = ctx.evaluate("""
B => A
D & E => B
G & H => F
I & J => G
G => H
L & M => K
O & P => L & N
N => M
""")
ans = ctx.evaluate("= D E I J O P")
ans = ctx.evaluate("A F K P")
self.assertEqual(ans, [True, True, True, True])
ans = ctx.evaluate("= D E I J P")
ans = ctx.evaluate("A F K P")
self.assertEqual(ans, [True, True, False, True])
def test_not(self):
ctx = Backward()
ans = ctx.evaluate("= a")
ans = ctx.evaluate("a")
self.assertEqual(ans, [True])
ans = ctx.evaluate("!a")
self.assertEqual(ans, [False])
ans = ctx.evaluate("!!a")
self.assertEqual(ans, [True])
ans = ctx.evaluate("!!(!a)")
self.assertEqual(ans, [False])
ans = ctx.evaluate("!b")
self.assertEqual(ans, [True])
def test_rule_samerule(self):
ctx = Backward()
ctx.evaluate("""
B => A
C => A
""")
ctx.evaluate("= B")
ans = ctx.evaluate("A")
self.assertEqual(ans, [True])
ctx.evaluate("= C")
ans = ctx.evaluate("A")
self.assertEqual(ans, [True])
ctx.evaluate("= B C")
ans = ctx.evaluate("A")
self.assertEqual(ans, [True])
def test_rule_xor(self):
ctx = Backward()
ctx.evaluate("""
B & C => A
D ^ E => B
B => C
""")
ctx.evaluate("=")
ans = ctx.evaluate("A")
self.assertEqual(ans, [False])
ctx.evaluate("= D")
ans = ctx.evaluate("A")
self.assertEqual(ans, [True])
ctx.evaluate("= E")
ans = ctx.evaluate("A")
self.assertEqual(ans, [True])
ctx.evaluate("= D E")
ans = ctx.evaluate("A")
self.assertEqual(ans, [False])
def test_rule_not2(self):
ctx = Backward()
ctx.evaluate("!A | A => B")
ctx.evaluate("A | !A => C")
ans = ctx.evaluate("B C")
self.assertEqual(ans, [True, True])
def test_rule_not1(self):
ctx = Backward()
ctx.evaluate("B & !C => A")
ctx.evaluate("=")
ans = ctx.evaluate("A")
self.assertEqual(ans, [False])
ctx.evaluate("= B")
ans = ctx.evaluate("A")
self.assertEqual(ans, [True])
ctx.evaluate("= C")
ans = ctx.evaluate("A")
self.assertEqual(ans, [False])
ctx.evaluate("= B C")
ans = ctx.evaluate("A")
self.assertEqual(ans, [False])
And initial facts:
Fritz croaks
Fritz eats flies
Our goal is to decide wether Fritz is green.
"""
if __name__ == "__main__":
ctx = Backward()
# Defining our knowledge base
ctx.evaluate("croaks & eatsFlies => frog")
ctx.evaluate("chirps & sings => canary")
ctx.evaluate("frog => green")
ctx.evaluate("canary => yellow")
# Initial facts
# ctx.evaluate("= croaks eatsFlies")
# Let's bind some questions to ask the user whenever the value of the variable is unknown.
ctx.bind_question("croaks", "Does it croak?")
ctx.bind_question("eatsFlies", "Does it eat flies?")
ctx.bind_question("chirps", "Does it chirp?")
ctx.bind_question("sings", "Does it sing?")
