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40 lines
917 B
Python
40 lines
917 B
Python
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import pytest # type: ignore
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from typing import List, Type
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from monads import Monad, Maybe, Result
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@pytest.fixture(scope="module", params=[Maybe, Result])
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def monad(request) -> Type:
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return request.param
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def test_bind(monad) -> None:
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expected: Monad[int] = monad.unit(2)
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assert expected == monad.unit(1).bind(lambda x: monad.unit(x + 1))
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def test_left_identity(monad) -> None:
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n: int = 3
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def f(n: int) -> Monad[int]:
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return monad.unit(n * 3)
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assert monad.unit(n).bind(f) == f(n)
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def test_right_identity(monad) -> None:
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m: Monad[int] = monad.unit(3)
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assert m == m.bind(lambda x: monad.unit(x))
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def test_associativity(monad) -> None:
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m: Monad[int] = monad.unit(3)
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def f(n: int) -> Monad[int]:
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return monad.unit(n * 3)
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def g(n: int) -> Monad[int]:
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return monad.unit(n + 5)
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assert m.bind(f).bind(g) == m.bind(lambda x: f(x).bind(g))
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