mirror of
https://github.com/correl/typesafe-monads.git
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93 lines
2.4 KiB
Python
93 lines
2.4 KiB
Python
import pytest # type: ignore
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from typing import Any, Callable, TypeVar
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from monads import Functor, Applicative, Reader
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from monads.reader import curry
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T = TypeVar("T")
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S = TypeVar("S")
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def test_functor_identity() -> None:
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m: Reader = Reader.pure(3)
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identity: Callable[[T], T] = lambda x: x
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assert m(0) == m.map(identity)(0)
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def test_functor_associativity() -> None:
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f: Callable[[int], int] = lambda x: x + 1
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g: Callable[[int], str] = lambda x: str(x)
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m: Reader[int, int] = Reader.pure(3)
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assert m.map(lambda x: g(f(x)))(0) == m.map(f).map(g)(0)
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def test_functor_map_mul_operator() -> None:
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m: Reader = Reader.pure(3)
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identity: Callable[[T], T] = lambda x: x
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assert m.map(identity)(0) == (m * identity)(0)
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def test_functor_map_rmul_operator() -> None:
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m: Reader = Reader.pure(3)
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identity: Callable[[T], T] = lambda x: x
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assert m.map(identity)(0) == (identity * m)(0)
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def test_applicative_fmap_using_ap() -> None:
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f: Callable[[int], int] = lambda x: x + 1
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m: Reader[int, int] = Reader.pure(3)
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assert m.map(f)(0) == m.apply(Reader.pure(f))(0)
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def test_monad_bind() -> None:
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expected: Reader[int, int] = Reader.pure(2)
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m: Reader[int, int] = Reader.pure(1)
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assert expected(0) == m.bind(lambda x: Reader.pure(x + 1))(0)
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def test_monad_bind_rshift_operator() -> None:
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m: Reader[int, int] = Reader.pure(2)
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f: Callable[[int], Reader[int, int]] = lambda x: Reader.pure(x + 1)
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assert m.bind(f)(0) == (m >> f)(0)
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def test_monad_left_identity() -> None:
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n: int = 3
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def f(n: int) -> Reader[int, int]:
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return Reader.pure(n * 3)
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m: Reader[int, int] = Reader.pure(n)
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assert m.bind(f)(0) == f(n)(0)
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def test_monad_right_identity() -> None:
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m: Reader[int, int] = Reader.pure(3)
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assert m(0) == m.bind(lambda x: Reader.pure(x))(0)
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def test_monad_associativity() -> None:
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m: Reader[int, int] = Reader.pure(3)
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def f(n: int) -> Reader[int, int]:
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return Reader.pure(n * 3)
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def g(n: int) -> Reader[int, int]:
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return Reader.pure(n + 5)
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assert m.bind(f).bind(g)(0) == m.bind(lambda x: f(x).bind(g))(0)
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def test_curry() -> None:
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def add3(a, b, c):
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return a + b + c
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assert add3(1, 2, 3) == curry(add3)(1)(2)(3)
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def test_call_curried_function_with_multiple_arguments() -> None:
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@curry
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def add3(a, b, c):
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return a + b + c
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assert add3(1, 2)(3) == add3(1, 2, 3)
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