Y combinator

y_combinator.cpp

#include <iostream>
#include <functional>
 
using namespace std;
 
// Y-combinator for the int type
function<int(int)> y(function<int(function<int(int)>, int)> f)
{ return bind(f, bind(&y, f), placeholders::_1); }
 
int main()
{
    // Y-combinator compatible factorial
    auto fact = [](function<int(int)> f, int v){ return v == 0 ? 1 : v * f(v - 1); };
    auto factorial = y(fact);
    cout << factorial(5) << endl;
    return 0;
}

http://handasse.blogspot.com/2010/05/c0xy.html