c++ - Using binder1st with custom functor -

i'd bind first argument of print functor 0:

#include<iostream> #include<functional> using namespace std;  class print : public std::binary_function<int,int,void>{ public:     void operator()(int val1, int val2)     {            cout << val1 + val2 << endl;     }    };  int main() {     print print;     binder1st(print,0) f; //this line 16     f(3);  //should print 3 } 

the program above (based on example c++ primer plus) not compile:

line16 : error : missing template arguments before ‘(’ token 

what wrong?

i don't want use c++11 nor boost features.

edited: operator() return type has been changed bool void simplicity

as error message says, missing template arguments before ( want

std::binder1st<print> f(print, 0); 

however, need make operator() const follows

bool operator()(int val1, int val2) const 

finally, function needs return something.