// passing an array name as a pointer (and printing it as a pointer)
// using it to update the array in place
// shows pointer arithmetic in an integer array

#include <iostream>
#include <iomanip>

using namespace std;

void subr (int* ip);

int main()
{

int ar[10] = {10, 20};
int* ip;

cout << "before:  ar[0] = " << ar[0] 
     << "  ar[1] = "        << ar[1] << endl;

cout << "address of ar is " << ar << endl;

ip = ar;
cout << "value at that address is " << *ip << endl << endl;

subr(ar);

cout << "after:   ar[0] = " << ar[0] 
     << "  ar[1] = "        << ar[1] << endl << endl;

subr(ar);

cout << "finally: ar[0] = " << ar[0] 
     << "  ar[1] = "        << ar[1] << endl;

return 0;
}

void subr (int* jp)
{ 

cout << endl << "subr says: value of pointer jp is " << jp << endl;
cout << "subr says: value at place jp points to is " << *jp 
     << endl << endl;

*jp = *jp + 1;

*(jp+1) = *(jp+1) + 2;

return;
}

/* output:

before:  ar[0] = 10  ar[1] = 20
address of ar is 0xffbefbb8
value at that address is 10

subr says: value of pointer jp is 0xffbefbb8
subr says: value at place jp points to is 10

after:   ar[0] = 11  ar[1] = 22

subr says: value of pointer jp is 0xffbefbb8
subr says: value at place jp points to is 11

finally: ar[0] = 12  ar[1] = 24

*/