#include <iostream>

using std::cout;
using std::endl;
using std::ostream;

int bin_srch(int ar[], int arsize, int desired_value);

int main() 

{

  int ar[10] = {10, 20, 30, 40, 50, 60, 70};   // rest unused
  int arsize = 7;    // number of entries in use
  int result;

  result = bin_srch(ar, 7, 30);
  if (result == -1)
    cout << "30 is not in array" << endl;
  else
    cout << "30 is at slot " << result << endl;
  
  result = bin_srch(ar, 7, 32);
  if (result == -1)
    cout << "32 is not in array" << endl;
  else
    cout << "32 is at slot " << result << endl;
  
  result = bin_srch(ar, 7, 10);
  if (result == -1)
    cout << "10 is not in array" << endl;
  else
    cout << "10 is at slot " << result << endl;
  
  result = bin_srch(ar, 7, 70);
  if (result == -1)
    cout << "70 is not in array" << endl;
  else
    cout << "70 is at slot " << result << endl;
  
  result = bin_srch(ar, 7, 72);
  if (result == -1)
    cout << "72 is not in array" << endl;
  else
    cout << "72 is at slot " << result << endl;
  
  return 0;
}

// ***********************************

int bin_srch(int ar[], int arsize, int desired_value)
{
  int lo, mid, hi;

  lo = 0;
  hi = arsize - 1;
  while (lo <= hi)
    {
      mid = (lo+hi)/2;
      if (ar[mid] == desired_value)
        return(mid);
      if (desired_value < ar[mid])
	hi = mid - 1;
      else
	lo = mid + 1;
    }
    return(-1);
}