new std::pair to_python_converter example

[SVN r27875]

example/std_pair.cpp

@@ -0,0 +1,46 @@
+// Copyright Ralf W. Grosse-Kunstleve 2002-2004. Distributed under the Boost
+// Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#include <boost/python/module.hpp>
+#include <boost/python/def.hpp>
+#include <boost/python/tuple.hpp>
+#include <boost/python/to_python_converter.hpp>
+
+namespace { // Avoid cluttering the global namespace.
+
+  // Converts a std::pair instance to a Python tuple.
+  template <typename T1, typename T2>
+  struct std_pair_to_tuple
+  {
+    static PyObject* convert(std::pair<T1, T2> const& p)
+    {
+      return boost::python::incref(
+        boost::python::make_tuple(p.first, p.second).ptr());
+    }
+  };
+
+  // Helper for convenience.
+  template <typename T1, typename T2>
+  struct std_pair_to_python_converter
+  {
+    std_pair_to_python_converter()
+    {
+      boost::python::to_python_converter<
+        std::pair<T1, T2>,
+        std_pair_to_tuple<T1, T2> >();
+    }
+  };
+
+  // Example function returning a std::pair.
+  std::pair<int, int>
+  foo() { return std::pair<int, int>(3, 5); }
+
+} // namespace anonymous
+
+BOOST_PYTHON_MODULE(std_pair_ext)
+{
+  using namespace boost::python;
+  std_pair_to_python_converter<int, int>();
+  def("foo", foo);
+}