def test_can_lookup_variable_from_the_environment(self): env = Environment() env.set("a", 2.0) env.set("b", 3.0) parse_tree = [ OperatorFactory.make_operator("*"), Symbol("a"), Symbol("b") ] result = Evaluator.evaluate(parse_tree, env) self.assertEqual(result, 6.0)
def test_can_handle_nested_arithmetic(self): parse_tree = [ OperatorFactory.make_operator("*"), Number(2.0), [ OperatorFactory.make_operator("+"), Number(4.0), Number(5.0) ] ] result = Evaluator.evaluate(parse_tree) self.assertEqual(result, 18.0)
def test_raises_exception_on_unknown_operator(self): with self.assertRaises(Exception) as context: OperatorFactory.make_operator("#") self.assertEqual(str(context.exception), 'Unknown operator: #')
def test_can_evaluate_simple_subtraction(self): parse_tree = [ OperatorFactory.make_operator("-"), Number(8.0), Number(4.0), Number(1.0) ] result = Evaluator.evaluate(parse_tree) self.assertEqual(result, 3.0)
def test_can_evaluate_simple_division(self): parse_tree = [ OperatorFactory.make_operator("/"), Number(8.0), Number(2.0) ] result = Evaluator.evaluate(parse_tree) self.assertEqual(result, 4.0)
def test_can_evaluate_simple_addition(self): parse_tree = [ OperatorFactory.make_operator("+"), Number(2.0), Number(3.0) ] result = Evaluator.evaluate(parse_tree) self.assertEqual(result, 5.0)
def test_can_set_variable_to_the_environment(self): env = Environment() parse_tree = [ OperatorFactory.make_operator("set!"), Symbol("x"), Number(19) ] Evaluator.evaluate(parse_tree, env) self.assertEqual(env.get("x"), 19)