# Make sure instances are registered import typeclasses.instances.list import typeclasses.instances.tuple import typeclasses.instances.function from typeclasses.instances.maybe import Nothing, Just from typeclasses.instances.tree import Branch, Leaf # The function we'll map f = lambda i: i + 1 # Instances # ========= # fmap on lists = map to list demo_list = [0, 1, 2, 3] assert fmap(f, demo_list) == [1, 2, 3, 4] # fmap on tuples = map to tuple demo_tuple = tuple(demo_list) assert fmap(f, demo_tuple) == (1, 2, 3, 4) # fmap on functions = function composition # fmap(f, g) = lambda x: f(g(x)) assert fmap(f, lambda i: i * 3)(1) == 4 # fmap on Maybe = function application on Just, Nothing on Nothing assert fmap(f, Nothing) == Nothing assert eq(fmap(f, Just(1)), Just(2)) # fmap on Tree = recursive fmap on branches, application on value in leafs # I.e., if the original is
def test_args_and_kwargs():
assert fmap(times2, ((1, 2), {'xs': [3, 4]})) == ((2, 4), {'xs': [6, 8]})
def __str__(self):
return 'Leaf %r' % self.value
def __repr__(self):
return 'Leaf %r' % self.value
class Branch(Tree):
def __init__(self, left, right):
self.left = left
self.right = right
def __str__(self):
return 'Branch (%r) (%r)' % (self.left, self.right)
def __repr__(self):
return 'Branch (%r) (%r)' % (self.left, self.right)
instance(Functor, Tree, lambda f, o: Leaf(f(o.value)) if isinstance(o, Leaf)
else Branch(fmap(f, o.left), fmap(f, o.right)))
instance(Eq, Tree,
lambda a, b:
a.value == b.value if (
isinstance(a, Leaf) and isinstance(b, Leaf))
else (eq(a.left, b.left) and eq(a.right, b.right)) if (
isinstance(a, Branch) and isinstance(b, Branch))
else False,
None)
def test_fmap_tuple():
assert fmap(times2, (1, 2, 3)) == (2, 4, 6)
def test_dict_of_list():
assert fmap(times2, {'xs': [1, 2, 3]}) == {'xs': [2, 4, 6]}
def test_fmap_range():
assert isinstance(fmap(times2, range(3)), t.Generator)
def test_fmap_set():
assert fmap(times2, {1, 2, 3}) == {2, 4, 6}
def test_fmap_list():
assert fmap(times2, [1, 2, 3]) == [2, 4, 6]
def test_fmap_frozenset():
assert fmap(times2, frozenset({1, 2, 3})) == frozenset({2, 4, 6})
def test_fmap_dict():
assert fmap(times2, {'a': 1, 'b': 2}) == {'a': 2, 'b': 4}
def test_fmap_btes():
assert fmap(times2, bytes([1, 2, 3])) == bytes([2, 4, 6])
def test_fmap_str():
assert fmap(times2, 'test') == 'tteesstt'