boost::function

 #  if BOOST_FUNCTION_MAX_ARGS >= 10
#    include <boost/function/function10.hpp>
#  endif
#else
// What is the '3' for?
#  define BOOST_PP_ITERATION_PARAMS_1 (3,(0,BOOST_FUNCTION_MAX_ARGS,<boost/function/detail/function_iterate.hpp>))
#  include BOOST_PP_ITERATE()
#  undef BOOST_PP_ITERATION_PARAMS_1
#endif