Re: [pygccxml-development] Proper overload resolution

[Benoit L. <ben...@mo...>]

Roman Yakovenko wrote:
> On Mon, May 17, 2010 at 6:23 PM, Benoit Leveau
> <ben...@mo...> wrote:
>> Hello,
>>
>> Consider the following class:
>>
>> struct MyClass
>> {
>> void setBool(bool a);
>> void setInt(int a);
>> };
>>
>> Because of the way the overloading resolution works currently in boost
>> python, if you're trying to bind these two functions to __setitem__,
>> only one of these functions (the last one bound actually) will always be
>> called, no matter if you call __setitem__ with a bool or an int (for
>> more information of the why, please take a look at the cplusplus-sig
>> thread mentioned below).
>>
>> The only way I could find to bind these two methods to __setitem__ and
>> have them called "correctly" is to bind them as two separate functions,
>> and then define a __setitem__ function in python at runtime, by adding
>> something like that in the __init__.py file:
>>
>> def custom_set_item(a):
>>  if isinstanceof(a, bool):
>>  ...
>>  ...
>>
>> MyClass.__setitem__ = custom_set_item
>>
>> Maybe there's a way to do that by binding a setitem which would take a
>> bp::object and test the type in C++, I haven't tried.
> 
> You can do this in C++ too, but why bother? You can generate that code
> from Py++ :-)
> 
>> It looks like Troy D. Straszheim came with a better implementation of
>> the overloading mechanism (which is much closer to what we expect):
>> http://mail.python.org/pipermail/cplusplus-sig/2009-December/015047.html
>>
>> It is apparently considered for addition in boost, but looks like
>> they're waiting for the new langbinding integration:
>> http://www.boost.org/doc/libs/1_43_0/libs/python/todo.html
>>
>> Any chance one of you have tried Troy's modification, or have any
>> suggestion for this problem?
> 
> Yes, I do. Please take a look on the following document(
> http://language-binding.net/pyplusplus/documentation/functions/registration_order.html
> ) and let me know whether it solved your problem or not.
> 

I already took a look at that page and:
- solution 1 doesn't work if you want to bind all the functions to one 
unique alias: __setitem__
- solution 2 & 3 don't change the fact that only one of the two 
functions will be called (as bool and int can be converted to each 
other, it's always the last one exposed that will be called)
- solution 4 is what I was mentionning in my message, but it doesn't 
seem py++ can generate that code yet. Or does it?