#include <iostream>
#include <assert.h>

using namespace std;

int sum2(int *data, int i, int j);
int find(int *data, int len, int x);

int main() {
  const int LEN = 5;
  int x[LEN] = {1, 2, 3, 4, 5};
  int indx;

  // sum2(x, 1, 3);
  // sum2(x, -2, 1);

  if ( (indx = find(x, LEN, 2)) < 0 )
    cerr << "Integer not found in array." << endl;
  else 
    cout << "Found 2 at " << indx << endl;

  if ( (indx = find(x, LEN, -4)) < 0 )
    cerr << "Integer not found in array." << endl;
  else
    cout << "Found -4 at " << indx << endl;

  return 0;
}


int sum2(int *data, int i, int j) {

  assert( i >= 0 && j >= 0 );

  return data[i] + data[j];
}


int find(int *data, int len, int x) {
  for ( int i = 0; i < len; i++ )
    if ( data[i] == x )
      return i;

  return -1;  // -1 for failure
}