def is_truthy(obj: objects.Object) -> bool:
if obj is objects.Null():
return False
elif obj is objects.Boolean(True):
return True
elif obj is objects.Boolean(False):
return False
else:
return True
def eval_array_index_exp(array: objects.Array,
index: objects.Integer) -> objects.Object:
idx = index.value
max_len = len(array.elements) - 1
if idx < 0 or idx > max_len:
return objects.Null()
return array.elements[idx]
def eval_bang_operator_exp(right: objects.Object) -> objects.Object:
if right is objects.Boolean(True):
return objects.Boolean(False)
elif right is objects.Boolean(False):
return objects.Boolean(True)
elif right is objects.Null():
return objects.Boolean(True)
else:
return objects.Boolean(False)
def eval_dict_index_exp(dictionary: objects.Dictionary,
index: objects.Object) -> objects.Object:
if not isinstance(index, objects.Hashable):
return objects.Error(f"unusable as dictionary key: {index.tp().value}")
pair = dictionary.pairs.get(index.hashkey(), None)
if pair is None:
return objects.Null()
return pair.value
def eval_if_exp(exp: ast.IfExpression,
env: objects.Environment) -> typing.Optional[objects.Object]:
condition = evaluate(exp.condition, env)
if is_error(condition) or condition is None:
return condition
if is_truthy(condition):
return evaluate(exp.consequence, env)
elif hasattr(exp, "alternative"):
return evaluate(exp.alternative, env)
else:
return objects.Null()
def _test_null_object(self, obj: objects.Object):
if obj is not objects.Null():
self.fail(f"Object is not NULL. Got {obj}.")