sum.cpp

#include <stdio.h>

template <typename T> T get_additive_identity(T* x) {};
template <> int get_additive_identity(int* x) { return 0;};
template <> double get_additive_identity(double* x) { return 0.0;};

template <typename T> T sum(T* X, int N) {
  T s = get_additive_identity(X);
  for (int i = 0; i < N; i++) {
    s += X[i];
  }
  return s;
}

#define ARRAYSIZE(x) (sizeof(x)/sizeof(x[0]))
int main(void) {
  int ai[] = {1,2,3,4,5};
  double ad[] = {1,2,3,4,5};
  int sumi;
  double sumd;

  sumi = sum(ai, ARRAYSIZE(ai));
  sumd = sum(ad, ARRAYSIZE(ad));
  printf("int: %d\n", sumi);
  printf("double: %f\n", sumd);
  return 0;
}