A while back I was going though the first chapters of Knuth’s The Art of Computer Programming and came across Euclid’s algorithm for finding the greatest common denominator. I decided to implement the algorithm as a C++ template. Here’s the complete example.

#include <iostream>

using namespace std;

template 
struct Euclids
{
  enum { value = Euclids::value };
};

template 
struct Euclids
{
  enum { value = N };
};

int main(int, char *[])
{
  cout << "GCD: 5,4: " << Euclids<5,4>::value << endl;
  cout << "GCD: 10, 5: " << Euclids<10, 5>::value << endl;
  cout << "GCD: 18, 8: " << Euclids<18, 8>::value << endl;
  cout << "GCD: 894744, 2312: " << Euclids<894744, 2312>::value << endl;
  cout << "GCD: 100, 10000: " << Euclids<100, 10000>::value << endl;
  cout << "GCD: 40, 50: " << Euclids<40,50>::value << endl;
}