Pythonで算術入門 ref: https://qiita.com/yhay81/items/de74be5abbb09f872183

file0.txt

class NaturalNumber:
    def __init__(self, p=None):
        self.predecessor = p

    def __eq__(self, x):
        if self.predecessor is None and x.predecessor is None:
            return True
        elif (self.predecessor is None and x.predecessor is not None) \
                or (self.predecessor is not None and x.predecessor is None):
            return False
        else:
            return self.predecessor == x.predecessor

file1.txt

    def __add__(self, x):
        if x == N_ZERO:
            return self
        else:
            return NaturalNumber(self + x.predecessor)

    def __mul__(self, x):
        if x == N_ZERO:
            return N_ZERO
        else:
            return self + self * x.predecessor

file2.txt

git clone https://github.com/yhay81/pythonic-algebra.git
cd pythonic-algebra
python -m unittest tests/test_natural_number.py
python -m unittest tests/test_integer.py
python -m unittest tests/test_rational.py
python
>>>from numbers.natural_number import *
>>>one = NaturalNumber(NaturalNumber())
>>>two = one + one
>>>three = two + one
>>>four = two * two
>>>n256 = four ** four
>>>x = n256 % three
>>>x == one
>>>for n in four:
>>>  print(n)