Function pointer example

#include <cstdio>


void apply(void (*FUN)(int &), int *begin, int *end) {
  for (int *p = begin; p != end; ++p) {
    (*FUN)(*p);
  }
}

void apply2(void FUN(int &), int *begin, int *end) {
  for (int *p = begin; p != end; ++p) {
    FUN(*p);
  }
}

void apply3(void (*FUN)(int &), int *begin, int *end) {
  for (int *p = begin; p != end; ++p) {
    FUN(*p);
  }
}

void apply4(void FUN(int &), int *begin, int *end) {
  for (int *p = begin; p != end; ++p) {
    (*FUN)(*p);
  }
}

void negate(int &i) {
  i = -i;
}

void print(int &i) {
  printf("%d ", i);
}
int main() {
  int a[] = {10, 0, -10, 9};
  const int N = sizeof(a) / sizeof(int);
  apply(negate, a, a + N);
  apply2(print, a, a + N);
  printf("\n");

  apply3(negate, a, a + N);
  apply4(print, a, a + N);
  printf("\n");

  return 0;
}