"Jonathan Brandmeyer" <jdbrandm@unity.ncsu.edu> writes:

I have a C++ type that I want to construct from a python tuple, and use python tuples in it's place. implicitly_convertible<Source, Target>() looked like the right thing, but it is not giving me the results that I had hoped. A complete example of what I am trying to do follows.

This particular run was tested with GCC 3.2.2 (mingw) with Boost.Python 1.30.0 and Python 2.2.2 on WinXP.

Thanks for you help, Jonathan Brandmeyer

--------------------- tuple_test.cpp------------------------ #include <boost/python.hpp>

class tuple_type { private: double x; double y; double z; public: tuple_type( double a=0.0, double b=0.0, double c=0.0) : x(a), y(b), z(c) {}

tuple_type( boost::python::tuple sequence) { using boost::python::extract;

int i = extract<int>( sequence.attr("__len__")); switch (i) { case 3: z = extract<double>( sequence[2]); // FALLTHROUGH case 2: y = extract<double>( sequence[1]); x = extract<double>( sequence[0]); break; default: break; } }

tuple_type operator+( const tuple_type& t) const { return tuple_type( x+t.x, y+t.y, z+t.z); } };

BOOST_PYTHON_MODULE( tuple_test) { using namespace boost::python;

class_<tuple_type>( "tuple_type", init<double, double, double>()) .def( self + self) ;

implicitly_convertible<tuple, tuple_type>(); }

I'm not sure what's going wrong here, but could you try this instead? #include <boost/python.hpp> class tuple_type { private: double x; double y; double z; public: tuple_type( double a=0.0, double b=0.0, double c=0.0) : x(a), y(b), z(c) {} tuple_type( boost::python::tuple sequence) { using boost::python::extract; int i = extract<int>( sequence.attr("__len__")); switch (i) { case 3: z = extract<double>( sequence[2]); // FALLTHROUGH case 2: y = extract<double>( sequence[1]); x = extract<double>( sequence[0]); break; default: break; } } tuple_type operator+( const tuple_type& t) const { return tuple_type( x+t.x, y+t.y, z+t.z); } }; BOOST_PYTHON_MODULE( tuple_test) { using namespace boost::python; class_<tuple_type>( "tuple_type", init<double, double, double>()) .def( self + self) .def( self + other<tuple>()) ; } -- Dave Abrahams Boost Consulting www.boost-consulting.com