Adds transducers support #904
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returns/transducers/tfilter.py
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| .. code:: python | ||
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| >>> from typing import List | ||
| >>> from returns.transducers import tfilter, reduce |
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Let's import reduce from functools, because user might be confused: is it our reduce or default one?
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We need to use our reduce since we have more features than the built-in reduce
| >>> assert reduce(xform, my_list, []) == [0, 2, 4, 6] | ||
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| """ | ||
| def reducer( |
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We tend to use decorator / factory naming when defining nested decorators
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Yep, but I think using that pattern might be weird:
def tmap(function):
def reducer(step):
def map_(acc, value):
...
return map_
return reducer
def tmap(function):
def decorator(step):
def factory(acc, value):
...
return map_
return reducerIn fact transducers is not intended to be use as a decorator and I think tmap -> reducer -> map_ is more meaningful! 🤔
| Callable[[_AccValueType, _ValueType], _AccValueType], | ||
| ]: | ||
| """ | ||
| :py:func:`filter <filter>` implementation on a transducer form. |
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Let's make the first line more user-friendly by removing :py:func: stuff.
It can be later in the body.
thepabloaguilar
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| #: A singleton representing any missing value | ||
| Missing = _Missing() |
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| Missing = _Missing() | |
| Missing: Final = _Missing() |
| from returns.transducers.transducers import _Missing | ||
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| def test_missing_singleton(): |
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| def test_missing_singleton(): | |
| def test_missing_singleton() -> None: |
And all other tests as well.
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| def test_reduce(): | ||
| """Should fail when iterable is empty and non initial value is given.""" |
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Should we? Raising exceptions is not something we do in this library (at least we try to).
Can we just return the empty sequence? Or do anything else?
I have made things!
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