C++11 scoped timer class and usage

scoped_timer.cpp

// C++11 scoped timer class and usage 
//
// an example of RAII 'resource acquisition is initialisation' idiom 
// build : g++ -Wall -std=c++11 -O5 -o scoped_timer scoped_timer.cpp 
//
// on linux x64 resolution of timer seems to be microseconds [ on win/VC it may be much worse ] 
//
// I like this approach as it doesnt litter your existing code with garbage, 
// although there might be some inaccuracy due to stack setup/pulldown of the timer class itself
//
// github.com/justgord
//
#include <functional>
#include <chrono>
#include <iostream>
 
using namespace std;
 
struct ScopedNanoTimer
{
    chrono::high_resolution_clock::time_point t0;
    function<void(int)> cb;
    
    ScopedNanoTimer(function<void(int)> callback)
        : t0(chrono::high_resolution_clock::now())
        , cb(callback)
    {
    }
    ~ScopedNanoTimer(void)
    {
        auto  t1 = chrono::high_resolution_clock::now();
        auto nanos = chrono::duration_cast<chrono::nanoseconds>(t1-t0).count();
 
        cb(nanos);
    }
};
 
 
// usage
 
int main()
{
    const int N=10000000;
 
    struct Results
    {
        void operator()(int ns)
        {
            cout << "Ops        : " << N << endl;
            cout << "Nanos      : " << ns << endl;
            cout << "ns per op  : " << (ns/N) << endl;
        }
    };
 
    Results results;
 
    ScopedNanoTimer Timer(results);
    
    // do some work you want to time
 
    long double sum=0.0;
    for (int i=0;i<N;i++)
    {
        sum += i*45.678;
    }
    cout << "Sum : " << sum << endl;
 
    return 0;
}