How do I return a closure from a function?

Question

I want my getEnd function to return a closure with start saved.

When I call this closure it should return time difference...

How to implement it in the c++?

Something like followed:

using namespace std;

long microtime() {
  timeval time;
  gettimeofday(&time, NULL);
  long microsec = ((unsigned long long)time.tv_sec * 1000000) + time.tv_usec;
  return microsec;
}


std::function<void()> getEnd (){
  long start = microtime();
  long end() {
    return microtime() - start;
  }
  return end;
};

Answer 1

#include <functional>
std::function<long()>  getEnd()
{
    long const start = microtime();
    return [=]{ return microtime() - start; };
}

Please note that the above will allocate memory on the heap, so for most practical applications a better alternative would be

struct timer {
     long const start;
     timer(): start(microtime()) {}
     long operator()() { return microtime - start();  }
};

timer getEnd() { return timer(); }