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43 lines
997 B
Python
43 lines
997 B
Python
from typing import Callable
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import pytest # type: ignore
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from monads import Monad
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from .fixtures import monad
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def test_bind(monad) -> None:
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expected: Monad[int] = monad.pure(2)
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assert expected == monad.pure(1).bind(lambda x: monad.pure(x + 1))
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def test_bind_rshift_operator(monad) -> None:
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m: Monad[int] = monad.pure(2)
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f: Callable[[int], Monad[int]] = lambda x: monad.pure(x + 1)
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assert m.bind(f) == m >> f
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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.pure(n * 3)
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assert monad.pure(n).bind(f) == f(n)
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def test_right_identity(monad) -> None:
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m: Monad[int] = monad.pure(3)
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assert m == m.bind(lambda x: monad.pure(x))
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def test_associativity(monad) -> None:
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m: Monad[int] = monad.pure(3)
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def f(n: int) -> Monad[int]:
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return monad.pure(n * 3)
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def g(n: int) -> Monad[int]:
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return monad.pure(n + 5)
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assert m.bind(f).bind(g) == m.bind(lambda x: f(x).bind(g))
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