test.py

from pipe_fn import e


# e is the identity mapping


def add(this, other):
    return this + other


print([1, 2, 3] | e / sum)
# sum([1, 2, 3])
# => 6

print([2, 3, -1] | e ** {'key': lambda x: -x} / sorted)  # set kwargs
# sorted([2, 3, -1], key=lambda x: -x)
# => [3, 2, -1]

print([[1], [2], [3]] | e / sum * ([],))  # set args


# sum([[1], [2], [3]], [])
# => [1, 2, 3]


def my_func(self, *args, **kwargs):
    return self, args, kwargs


print([1, 2, 3]
      | e
      ** dict(a=1, b=2, c=3)  # you should set kwargs first because of the high priority of `**` operator.

      * (4, 5, 6)  # it'okay to change the order of setting `args` and setting `function`.
      / my_func)
# => ([1, 2, 3], (4, 5, 6), {'a': 1, 'b': 2, 'c': 3})


print(1 | e / add * (1,))


# add(1, 1)
# => 2


def double(x):
    return 2 * x


# and then composition
print(1 | (e / add * (2,) + double + double))
# double(double(add(1, 2))
# => 12 = (1 + 2) * 2 * 2


# set single arg
[['a'], ['b']] | e / sum @ [] | e / print
# print(sum([['a'], ['b']], []))
# => [1, 2]