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Comment Re:Python and D (Score 1) 570

There's no way that I can see to do this automatically.

The concern is this (reposted here so people don't have to dig through Pyd's docs):

class Foo {
    void bar() { writefln(""); }

void func(Foo f) {; }

When we wrap this class and this function with Pyd (or Boost.Python), we can subclass Foo with a Python class:

class PyClass(Foo):
    def bar(self):
        print ""

The behavior we want is:

>>> o = PyClass()
>>> func(o)

However, there's no way to get the D function to polymorphically call the Python subclass's method without user intervention. I cannot generate the required wrapper with templates alone. Therefore, users must write thin wrapper classes in D, and expose the wrappers to Python:

class FooWrap : Foo {
    mixin OverloadShim;
    void bar() {
        get_overload(&, "bar");

get_overload performs a bit of magic, checking if the current object is an actual instance of FooWrap or a Python subclass, and calling the proper method as appropriate.

In the dim and distant future, I may be able to generate code like this in a SWIG-like fashion. D is remarkably easy to parse (perhaps one of the language's strongest advantages over C++), and I have almost completed a D parser written in Python (using Pyparsing). Since Pyd's build utility is written in Python, doing this kind of trickery shouldn't prove too difficult.

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