boost::function map with different return types

Hi, I have the following code: --------------- #include #include #include <map> #include <string> class Foo { public: void Function3() const { int i =2; }; const std::string Function4() const { return ""; }; unsigned int Function5() const { return 2; }; }; std::map functions; Foo foo; functions["Function3"] = boost::bind(&Foo::Function3, &foo); functions["Function4"] = boost::bind(&Foo::Function4, &foo); functions["Function5"] = boost::bind(&Foo::Function5, &foo); // call the functions functions["Function4"](); -------------- Calling the correct function with the entries in the map is no problem, but how can I get the return value. I tried something like that: "unsigned int i = functions["Function5"]();" but sadly it doesnt work, maybe cause in the map I declared for the return value "void"? How can I have such a map where to have functions with different return types in it and to get the return value after a call of the function through the map? Thanks in advance Julia