On Mon, Dec 20, 2021 at 12:44 PM <asleep.c...@gmail.com> wrote:
> This is such a great idea that I think it deserves its own PEP (to compete
> with this one?) Let me explain. PEP 677 was created for the sole purpose of
> replacing typing.Callable, but there are still some other areas where
> function metadata is required. What if we instead introduced a function
> prototype that allows you to "declare" a "function" without a body.
>
> typing example:
>
> import typing
>
> @typing.Callable
> def IntToIntFunc(a: int) -> int
>
> def flat_map(
> l: list[int],
> func: IntToIntFunc
> ) -> list[int]:
> ...
>
> ctypes example:
>
> import ctypes
>
> @ctypes.CFUNCTYPE
> def f(x: int) -> bool
>
> But of course this comes with a few issues: should it be an expression and
> if so, should the name be optional? How can ParamSpec be handled?
>
Allowing 'def' without a body based on the presence or absence of a
decorator sounds like it will just confuse people and cause bizarre errors
if people accidentally leave out a body. Let's not go there.
However, Lukasz has already proposed a very similar mechanism (with dummy
body), without needing a decorator. His proposal is simply:
def IntToIntFunc(a: int) -> int: ...
def flat_map(l: list[int], func: IntToIntFunc) -> list[int]:
# body
No need for a `@Callable` decorator!
--
--Guido van Rossum (python.org/~guido)
*Pronouns: he/him **(why is my pronoun here?)*
<http://feministing.com/2015/02/03/how-using-they-as-a-singular-pronoun-can-change-the-world/>
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