def to_maybe(self):
"""
Transform Box into not empty Maybe.
:returns: non empty Maybe monad with previous value
:rtype: Maybe[A]
"""
from pymonet.maybe import Maybe
return Maybe.just(self.value)
def to_maybe(self, *args):
"""
Transform Lazy into not empty Maybe with constructor_fn result.
:returns: not empty Maybe monad with constructor_fn result
:rtype: Maybe[A]
"""
from pymonet.maybe import Maybe
return Maybe.just(self.get(*args))
def to_maybe(self):
"""
Transform Either to Maybe.
:returns: Maybe with previous value
:rtype: Maybe[A]
"""
from pymonet.maybe import Maybe
return Maybe.just(self.value)
def to_maybe_test(self):
if self.is_fail:
assert self.monad(self.value).to_maybe() == Maybe.nothing()
else:
assert self.monad(self.value).to_maybe() == Maybe.just(self.value)
def test_maybe_if_filter_returns_true_method_should_return_self():
assert Maybe.just(42).filter(lambda value: value % 2 == 0) == Maybe.just(
42)
def test_maybe_monad_law(integer):
MonadLawTester(monad=Maybe.just,
value=integer,
mapper1=lambda value: Maybe.just(value + 1),
mapper2=lambda value: Maybe.just(value + 2)).test()
def test_maybe_is_nothing_should_return_proper_boolean(integer):
assert Maybe.just(integer).is_nothing is False
assert Maybe.nothing().is_nothing is True
def test_maybe_if_filter_returns_false_method_should_return_empty_maybe():
assert Maybe.just(41).filter(
lambda value: value % 2 == 0) == Maybe.nothing()
def test_maybe_bind_should_retrun_result_of_mapper_called_with_maybe_value(
maybe_spy):
assert Maybe.just(42).bind(increase) == 43
def test_maybe_get_or_else_method_should_return_maybe_value_when_monad_is_not_empty(
integer):
assert Maybe.just(integer).get_or_else(0) is integer
def test_maybe_map_operator_should_be_applied_only_on_just_value(integer):
assert Maybe.just(42).map(increase) == Maybe.just(43)
assert Maybe.nothing().map(increase) == Maybe.nothing()
def test_maybe_eq_operator_should_compare_values(integer):
assert Maybe.just(integer) == Maybe.just(integer)
assert Maybe.just(None) == Maybe.just(None)
assert Maybe.just(integer) != Maybe.nothing()
def binder(self, value):
return Maybe.just(value + 1)
def test_maybe_ap_on_empty_maybe_should_not_be_applied():
def lambda_fn():
raise TypeError
assert Maybe.nothing().ap(Maybe.just(lambda_fn)) == Maybe.nothing()
assert Maybe.just(42).ap(Maybe.nothing()) == Maybe.nothing()
def test_maybe_functor_law(integer):
FunctorLawTester(functor=Maybe.just(integer),
mapper1=lambda value: value + 1,
mapper2=lambda value: value + 2).test()