python で関数合成的な何か

関数合成的な何か

$ python -V
Python 3.8.6

a.py

import functools

class F:
    @staticmethod
    def __cmp(f1, f2):
        def __i1(*args1, **kwargs1):
            def __i2(*args2, **kwargs2):
                return f1(*args2, **kwargs2)
            return f2(__i2(*args1, **kwargs1))
        return __i1


    @classmethod
    def composite(cls, *fs):
        return functools.reduce(cls.__cmp, fs)

test

a_test.py

import pytest
import functools

from a import F

def test_args1():
    """1引数の関数合成"""
    def d1(a):
        r = a * 2
        print(f"d1: {a} * 2 = {r}")
        return r

    def d2(a):
        r = a + 1
        print(f"d2: {a} + 1 = {r}")
        return r

    def d3(a):
        r = a // 3
        print(f"d3: {a} / 3 = {r}")
        return r

    f = F.composite(d1, d2, d3, d1, d2)
    assert f(123) == 165

def test_args2():
    """2引数以上はできないので適当にカリー化するとよい"""
    def d1(a, b):
        r = a * b
        print(f"d1: {a} * {b} = {r}")
        return r

    def d2(a, b):
        r = a + b
        print(f"d2: {a} + {b} = {r}")
        return r

    d3 = functools.partial(d1, b=2)
    d4 = functools.partial(d2, b=1)
    d5 = functools.partial(d1, b=3)
    d6 = functools.partial(d2, b=4)

    f = F.composite(d3, d4, d5, d6)
    assert f(123) == 745


def test_args3():
    """2引数以上は(ry"""
    def d1(a, b, c):
        r = a // b - c
        print(f"d1: {a} // {b} - {c} = {r}")
        return r

    def d2(a, b, c):
        r = (a + b) ** c
        print(f"d2: ({a} + {b}) ** {c} = {r}")
        return r

    d3 = functools.partial(d1, b=5, c=5)
    d4 = functools.partial(d2, b=3, c=2)
    d5 = functools.partial(d1, b=345, c=3)
    d6 = functools.partial(d2, b=4, c=8)

    f = F.composite(d3, d4, d5, d6)
    assert f(123) == 256

run test

bash

$ pytest -V
pytest 6.1.2

$ pytest -s -v a_test.py
=============================================== test session starts ===============================================
platform darwin -- Python 3.8.6, pytest-6.1.2, py-1.9.0, pluggy-0.13.1 -- /Users/kuryu/.pyenv/versions/3.8.6/bin/python3.8
cachedir: .pytest_cache
rootdir: /Users/kuryu/workspace/work
plugins: Faker-4.16.0
collected 3 items

a_test.py::test_args1 d1: 123 * 2 = 246
d2: 246 + 1 = 247
d3: 247 / 3 = 82
d1: 82 * 2 = 164
d2: 164 + 1 = 165
PASSED
a_test.py::test_args2 d1: 123 * 2 = 246
d2: 246 + 1 = 247
d1: 247 * 3 = 741
d2: 741 + 4 = 745
PASSED
a_test.py::test_args3 d1: 123 // 5 - 5 = 19
d2: (19 + 3) ** 2 = 484
d1: 484 // 345 - 3 = -2
d2: (-2 + 4) ** 8 = 256
PASSED

================================================ 3 passed in 0.06s ================================================

カレー食べたい。