How about instead of omitting the body, it contains a single expression, say: def int(x: float): -> float typing.Prototype It doesn’t totally break protocol to have a function complie differently depending on its content— that’s done with generator functions. -CHB On Thu, Dec 23, 2021 at 7:20 AM <asleep.cult@gmail.com> wrote:
Hello
In thread about PEP 677, I (with the help of another proposal) came up with an alternative to typing.Callable called function prototypes. The basic concept is to create a function prototype object when the body of a function is omitted.
The thread can be found here: https://mail.python.org/archives/list/python-dev@python.org/thread/OGACYN2X7...
Mark Shannon initially proposed that functions be used as types and provided this example:
@Callable def IntToIntFunc(a:int)->int: pass
def flat_map( l: list[int], func: IntToIntFunc ) -> list[int]: ....
I further proposed that we make the body of a function non-mandatory and create a function prototype if it is omitted. I provided these examples:
import typing
@typing.Callable def IntToIntFunc(a: int) -> int
def flat_map( l: list[int], func: IntToIntFunc ) -> list[int]: ...
import ctypes
@ctypes.CFUNCTYPE def f(x: int) -> bool
I have since taken it upon myself to implement this in a fork of cpython: https://github.com/asleep-cult/cpython
To remain consistent with function definitions, I have also added an alternative lambda syntax that allows you to annotate arguments and the return type. The syntax requires you to parenthesize the argument list:
lambda (a: int, b: int) -> int: ...
This new lambda syntax also allows you to create a function prototype by omitting the body. The original example can be rewritten as follows:
def flat_map( l: list[int], func: lambda (a: int) -> int ) -> list[int]: ...
Problems: - It is not possible to use ParamSpec with this - The lambda prototype syntax might be jarring - Some people might accidentally forget the function body
Here is some feedback that I have already collected:
"Yeah, making the body optional (without looking at decorators) is not acceptable either. Too easy to do by mistake (I still do this All. The. Time. :-)" - Guido van Rossum
"i would strongly prefer this over the existing pep" - Ronny Pfannschmidt
"I find this unnecessary and unreadable.
Python isn't C or Java." - BundleOfJoysticks (Reddit) _______________________________________________ Python-Dev mailing list -- python-dev@python.org To unsubscribe send an email to python-dev-leave@python.org https://mail.python.org/mailman3/lists/python-dev.python.org/ Message archived at https://mail.python.org/archives/list/python-dev@python.org/message/B6VKYV5T... Code of Conduct: http://python.org/psf/codeofconduct/
-- Christopher Barker, PhD (Chris) Python Language Consulting - Teaching - Scientific Software Development - Desktop GUI and Web Development - wxPython, numpy, scipy, Cython