/* Lecture code 15.1
 *
 * Time trial pitting a regular C++ function against a C++ functor.
 * (Hint: the functor wins!)  Make sure you enable compiler optimization
 * before running this program; otherwise the results won't be
 * particularly impressive.
 */

#include <iostream>
#include <vector>
#include <ctime>
#include <algorithm>
using namespace std;

const size_t kNumElems = 100000;
const size_t kNumTests = 1;

bool CompareBackwards(int one, int two)
{
	return two < one;
}

void RunFunctionTest(const vector<int>& source)
{
	vector<int> myContainer = source;
	
	clock_t start = clock();

	for(size_t h = 0; h < kNumTests; h++)
	{
		sort(myContainer.begin(), myContainer.end(), CompareBackwards);
	}

	start = clock() - start;

	cout << "Regular function finished in ";
	cout << ((double)(start) / CLOCKS_PER_SEC);
	cout << " seconds." << endl;
}

class CompareBackwardsFunctor
{
public:
	bool operator() (int one, int two) const
	{
		return two < one;
	}
};

void RunFunctorTest(const vector<int>& source)
{
	vector<int> myContainer = source;

	clock_t start = clock();

	for(size_t h = 0; h < kNumTests; h++)
	{
		sort(myContainer.begin(), myContainer.end(), CompareBackwardsFunctor());
	}

	start = clock() - start;

	cout << "Custom functor finished in ";
	cout << ((double)(start) / CLOCKS_PER_SEC);
	cout << " seconds." << endl;
}

int main()
{
	vector<int> sourceVector(kNumElems);
	generate(sourceVector.begin(), sourceVector.end(), rand);

	RunFunctionTest(sourceVector);
	RunFunctorTest(sourceVector);

	return 0;
}