def test_apply():
# applying arguments to f object returns partial applied functions.
# when apply one by one, it's called currying.
assert add.apply(1).apply(2)() == 3
assert sub.apply(1).apply(2)() == -1
# apply can accept more than one arguments at a time
add_1_4 = add.apply(1, 4)
assert add_1_4 == 5
# supports keyword arguments as well, notice named argument 'base' is
# supposed to be the second argument of int
from_hex = f(int).apply(base=16)
assert from_hex('0a') == 10
assert from_hex('0b') == 11
assert from_hex('0c') == 12
assert from_hex('0d') == 13
assert from_hex('0e') == 14
assert from_hex('0f') == 15
assert from_hex('10') == 16
def test_value():
# a read-only property 'value' on f object, will invoke the function as
# well
assert add.apply(3, 8).value == 11