[C++-sig] [c++-sig] Making a Python tuple from a Boost.Fusion sequence

[Bruno Lalande]

Hello,

The topic below was opened in the Boost development mailing list,
where it's been pointed out to me that it fits better here.

You can also read the thread archive:
http://thread.gmane.org/gmane.comp.lib.boost.devel/186573

Regards
Bruno


---------- Forwarded message ----------


Hello,

I have written a little function that converts any Boost.Fusion
sequence into a Python tuple (boost::python::tuple). If a sub-sequence
is nested in the sequence, the result will also be a nested tuple (for
instance, boost::make_tuple(0, std::make_pair(1, 2), 3) will give (0,
(1, 2), 3) in Python).

The source code is attached to this mail.

The principle is that any sequence previously adapted to Boost.Fusion
will become a tuple in Python. So, by including the right
boost/fusion/adapted/xxx header, one can convert a pair, a tuple, a
boost::array, and obviously any of the sequences provided by
Boost.Fusion. For example:

#include <boost/python.hpp>
#include <boost/fusion/adapted/std_pair.hpp>
#include <boost/fusion/adapted/boost_tuple.hpp>
#include <boost/fusion/container/generation/make_vector.hpp>
#include "make_tuple_from_fusion_sequence.hpp"

using namespace boost::python;

tuple from_sequence()
{
   return make_tuple_from_fusion(
              boost::fusion::make_vector(
                 1,
                 std::make_pair("first", "second"),
                 2,
                 boost::make_tuple('a', 'b', 'c'),
                 3
              )
          );
}

BOOST_PYTHON_MODULE(mymodule)
{
   def("from_sequence", &from_sequence);
}


In Python we get:

>>> import mymodule
>>> mymodule.from_sequence()
(1, ('first', 'second'), 2, ('a', 'b', 'c'), 3)


Is there any interest in adding this function into Boost.Python? If
yes, I can write the doc and tests, clean the source and maybe improve
the implementation (for example, I feel that I could avoid the use of
m_iteration with a better use of Boost.Fusion...).


Regards
Bruno
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