Coroutines are now in Clang trunk, libc++

Re:Coroutines are now in Clang trunk, libc++ by amelius on Friday May 26, 2017 @10:58AM (#14424495)

But Python 2.7 has this problem:

    def f():
        x = 0

        def add(amount):
            x += amount # UnboundLocalError: local variable 'x' referenced before assignment

        add(10)
        add(20)
        add(30)

        return x


    print f()

In C++, this problem doesn't exist.

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Re:Coroutines are now in Clang trunk, libc++ by dmix on Friday May 26, 2017 @11:10AM (#14424576)

The question is the cost of supporting it (assuming this is a problem needing fixing) as it has far reaching implications in all of the added complexity to all the abstractions layered on top of it.

I'm not making a good/bad argument that one is better than the other. The two languages have widely different usecases and rationale in the language design. But I'm not convinced C++ is (or can become) very Pythonic given the complexity it must support at all the basic levels.

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Re:Coroutines are now in Clang trunk, libc++ by Veedrac on Friday May 26, 2017 @11:54AM (#14424916)

Python 3 release date: 3 December 2008

C++11 release date: 12 August 2011

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Re:Coroutines are now in Clang trunk, libc++ by amelius on Friday May 26, 2017 @03:55PM (#14426701)

True, but in C++ the problem never existed.

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Re:Coroutines are now in Clang trunk, libc++ by js2 on Friday May 26, 2017 @11:19AM (#14424655)

This is fixed in Python 3 with the nonlocal keyword. In Python 2, the idiomatic work-around is to have x be list of one item:

    def f():
        x = [0]
        def add(amt):
            x[0] += amt
        add(10)
        return x[0]

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