lambda and variable arguments in c++11

sample.cpp

#include <functional>
#include <iostream>

template<typename T>
void log(T arg)
{
  std::cout << arg;
  std::cout << std::endl;
}

template<typename T, typename... Args>
void log(T arg, Args... args)
{
  std::cout << arg << " ";
  log(args...);
}

template<typename T, typename U>
U map(std::function<U(T)> fn, T value)
{
  log("Map function:", value, value);
  return fn(value);
}

int main(int, char**)
{
  std::function<int(int)> fn = [](int a) { return a + 2; };

  std::cout << map(fn, 10) << std::endl;
  
  return 0;
}