EmptyCrate Software. Travel. Stuff.

The first Project Euler problem is to calculate the sum of all integers below 1000 which are divisible by either 3 or 5.

My solution is implemented entirely in C++ templates. The value is recursively calculated at compile time. The template specialization struct Problem1<0> stops the recursion and returns 0.

To compile this code with gcc you must expand the maximum allowed template recursion depth to at least 1000.

g++ EulerProblem1.cpp -ftemplate-depth-1000

//EulerProblem1.cpp
#include <iostream>
 
template<int count>
struct Problem1
{
  static const int value = (((count % 3) == 0 || (count % 5) == 0)?count:0) + Problem1<count - 1>::value;
};
 
template<>
struct Problem1<0>
{
  static const int value = 0;
};
 
int main()
{
  std::cout << Problem1<999>::value << std::endl;
}