[C++-sig] std::list wrapper [Was: Segfaults in object deallocation]

[Alex Leach]

On Wed, 20 Mar 2013 16:53:55 -0000, Alex Leach <beamesleach at gmail.com>  
wrote:

> On Wed, 20 Mar 2013 16:34:00 -0000, Jim Bosch <talljimbo at gmail.com>  
> wrote:
>
>>
>> [...] I'm curious what you're using to wrap std::list, as you clearly  
>> have methods that return std::list, and the standard library can be  
>> tricky to translate to Python due to things like iterator invalidation.
>
> Heh, not yet anyway! Although I've laid out the foundations, I haven't  
> yet implemented my attempt at a solution, nor tested it,

I've since got around to fixing the std::list wrapper I think I sent  
around before. Lots of errors in that version! Now, I've got it working,  
though; its sort and reverse functions use C++ STL algorithms instead of  
Python's, but that's probably a good thing; results appear to be  
consistent with those on a normal Python list. That said, I haven't  
profiled it for speed and compared performance against Python lists.

I attach a complete example in the attached zip archive; just run 'python  
test_make_list.py' to compile an example extension, which exposes  
std::list<int> and std::list<std::string>. Unit-tests are then run to  
compare those against identical Python lists.

make_list.zip contents:-

  ./test_make_list.py			 // Compiles example code and runs unit-tests
  ./test_make_list.cpp			 // example showing how to expose list<string> and  
list<int>
  ./boost_helpers/make_list.hpp      // defines  
boost::python::list_indexing_suite
  ./boost_helpers/make_callback.hpp  // needed for sort and reverse  
optional binary predicate
  ./util.py  						// helper functions for compiling with distutils

A couple things to mention:-

  1.  make_callback.hpp isn't as tidy as make_list.hpp; it probably  
shouldn't even be necessary, but I needed something to help calling back  
into Python code, and this seemed to work. I wrote quite a nice template  
implementation using variadic templates, but the C++98 alternative isn't  
great.

  2.  I haven't (yet) exposed a good initialiser for the list classes, so  
it's not possible to do, e.g.
    >>> int_list = test_make_list.IntList([1, 2, 3])

   Instead, I've been populating lists like this:-
    >>> int_list = test_make_list.IntList()
    >>> int_list[:] = [1, 2, 3]

Obviously, that's not quite ideal. Any help or advice with making a  
templatised initialiser would be very welcome though!

Kind regards,
Alex
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