The bind documentation mentions the apply object as a way to get around the fact that bind does not evaluate its first arguement. There is another use. You can reverse the roles of function and parameters. You can use apply and bind to turn a parameter into a functor, and call it using a function as a parameter! Example. #include <boost/bind.hpp> #include <boost/function.hpp> #include <boost/bind/apply.hpp> #include <fstream> #include <iostream> #include <iomanip> // some sample test functions. (data) int g(int x) {return x+1;}; int h(int x) {return x*x; }; int main(int argc, char * argv) { // want to work with functions of the form int f(int); typedef int P(int); // bind the integer 5 to apply turning // apply into the number 5 into a function! call it five boost::function<int (P)> five = boost::bind(boost::apply<int>(),_1,5); //int y = five(g); // Now call 5 with the "data" g and h. std::cout << "+1=" << five(g) << std::endl << "square = " << five(h) << std::endl; return 0; }; Results: +1=6 square = 25 -- Paul Elliott 1(512)837-1096 pelliott@io.com PMB 181, 11900 Metric Blvd Suite J http://www.io.com/~pelliott/pme/ Austin TX 78758-3117