async def test_flat_map_monad():
m = unit(42)
async def mapper(x):
return unit(x * 10)
a = await run(flat_map(mapper, m))
b = await run(unit(420))
assert a == b
async def test_flat_map_monad_law_associativity():
# (m >>= f) >>= g is just like doing m >>= (\x -> f x >>= g)
m = unit(42)
async def f(x):
return unit(x + 1000)
async def g(y):
return unit(y * 333)
async def h(x):
return flat_map(g, await f(x))
zs = flat_map(f, m)
a = await run(flat_map(g, zs))
b = await run(flat_map(h, m))
assert a == b
async def test_flat_map_monad_law_right_identity():
# m >>= return is no different than just m.
m = unit("move on up")
async def aunit(x):
return unit(x)
a = await run(flat_map(aunit, m))
b = await run(m)
assert a == b
async def test_flat_map_monad_law_left_identity():
# return x >>= f is the same thing as f x
x = 3
async def f(x):
return unit(x + 100000)
a = await run(flat_map(f, unit(x)))
b = await run(await f(x))
assert a == b
async def test_flap_map_done():
xs = AsyncStream()
result = []
async def asend(value):
nonlocal result
result.append(value)
async def mapper(value):
return from_iterable([value])
ys = flat_map(mapper, xs)
obv = AsyncAnonymousObserver()
await subscribe(ys, obv)
await xs.asend(10)
await xs.asend(20)
await xs.aclose()
await obv
assert obv.values == [(0, 10), (0, 20), (0, )]
async def h(x):
return flat_map(g, await f(x))