The file <boost/bind/placeholders.hpp> now contains nine of them, from _1 to _9. Would it be possible to increase the number, perhaps conditionally? I run into the problem with Luabind (Boost.Python like wrapper for Lua). In Lua it is possible to return multiple values like: result1, res2, res3 = foo(parameter1, par2, par3); Luabind internal machinery in this case uses 6 placeholders. /Pavel