def balanced_btree(frdm, size):
"""
Generates a random balanced tree of the given ``size``.
Each element is generated by a call to ``frdm``.
``size`` should be strictly positive.
:param frdm: callable
:param size: int
:return: BTree
"""
current_size = 1
btr = Leaf(frdm())
while current_size < size:
bt2 = btr.map(lambda x: frdm(), lambda x: frdm())
btr = Node(frdm(), btr, bt2)
current_size = 2 * current_size + 1
return btr
def test_map_leaf():
bt = Leaf(1)
res = bt.map(lambda x: x + 1, lambda x: x - 1)
exp = Leaf(2)
assert exp == res