C++ function and bind examples

                    /*

binders.cpp
-----------

Usage of function and bind.

Compile with
	g++ --std=c++11 -obinders binders.cpp
 
*/


#include <functional>
#include <iostream>
#include <string>


using namespace std;


// free function
float divide(int a, int b)
{
    return float(a) / b;
}


// struct with methods
struct Printer
{
    Printer(string s) : _s(s)
    {
    }
	
    string print()
    {
        return _s;
    }
    
    void hello(string s)
    {
        cout << s << endl;
    }
    
private:
    
    string _s;
};


// struct with overloaded methods
struct Logger
{
    Logger(string s) : _s(s)
    {
    }

    string print()
    {
        return _s;
    }
    
    string print(string s)
    {
        _s = s;
        return _s;
    }
    
private:
    
    string _s;
};


// functor
struct Multiplier
{
    int operator()(int x, int y)
    {
        return x * y;
    }
};


int main()
{
    using namespace std::placeholders; // for _1, _2, ...

    Printer p("Hello, World!");
    Logger l("Hello, World!");
    Multiplier m;

    // free function to function
    function<float(int, int)> f_div = divide;
    cout << "f_div(1, 2)=" << f_div(1, 2) << endl;
    
    // member function to function
    function<string(Printer*)> f1_print = &Printer::print;
    cout << "f1_print(&p)=" << f1_print(&p) << endl;
    
    function<void(Printer*, string)> f2_print = &Printer::hello;
    cout << "f2_print(&p, \"Hello, World!\")=";
    f2_print(&p, "Hello, World!");

    // member overloaded function to function
    function<string(Logger*)> f1_log = static_cast<string(Logger::*)()>(&Logger::print);
    cout << "f1_log(&l)=" << f1_log(&l) << endl;
    
    function<string(Logger*, string)> f2_log = static_cast<string(Logger::*)(string)>(&Logger::print);
    cout << "f2_log(&l, \"Hello, World!\")=" << f2_log(&l, "Hello, World!") << endl;
    
    // functor to function
    function<int(int, int)> f_multi = Multiplier();
    cout << "f_multi(2, 3)=" << f_multi(2, 3) << endl;

    // lambda to function
    function<float(float, float)> fl_div = [](float x, float y) -> float { divide(x, y); };
    cout << "fl_div(2, 2)=" << fl_div(2, 2) << endl;
    
    // free function binders
    cout << "bind(divide, 1, 2)()=" << bind(divide, 1, 2)() << endl;
    cout << "bind(divide, _1, 2)(3)=" << bind(divide, _1, 2)(3) << endl;
    cout << "bind(divide, 2, _1)(3)=" << bind(divide, 2, _1)(3) << endl;
    cout << "bind(divide, _2, _1)(3, 1)=" << bind(divide, _2, _1)(3, 1) << endl;
    cout << "bind(divide, _1, _1)(5)=" << bind(divide, _1, _1)(5) << endl;
    
    // bind free function to function
    function<float(int, int)> b1_div = bind(divide, _1, _2);
    cout << "b1_div(4, 2)=" << b1_div(4, 2) << endl;
    
    // bind free function to function; arguments copied, so new arguments do not affect the result
    function<float(int, int)> b2_div = bind(divide, 5, 2);
    cout << "b2_div(5, 2)=" << b2_div(4, 2) << endl;
    
    // functor binders
    cout << "bind<int>(m, _1, _2)(3, 4)=" << bind<int>(m, _1, _2)(3, 4) << endl;
    
    // bind functor to function
    function<int(int, int)> b_multi = bind<int>(m, _1, _2);
    cout << "b_multi(2, 5)=" << b_multi(2, 5) << endl;
    
    // member function binders
    cout << "bind(&Printer::print, ref(p))()=" << bind(&Printer::print, ref(p))() << endl;
    cout << "bind(&Printer::hello, ref(p), _1)(\"Hello\")=";
    bind(&Printer::hello, ref(p), _1)("Hello");
    cout << "bind(static_cast<string(Logger::*)()>(&Logger::print), ref(l))()=" << bind(static_cast<string(Logger::*)()>(&Logger::print), ref(l))() << endl;
    cout << "bind(static_cast<string(Logger::*)(string)>(&Logger::print), ref(l), _1)(\"Yaba daba doo\")=" <<
        bind(static_cast<string(Logger::*)(string)>(&Logger::print), ref(l), _1)("Yaba daba doo") << endl;

    return 0;
}