// FILE: pointer.cpp
// PURPOSE: Use pointer variables
//---------------------------------------------------------------------
// COMPILATION INSTRUCTIONS: g++ and gxx 
// COMMAND LINE: g++ (or gxx) pointerS.cpp
//=============================================================
// INSTRUCTIONS: 
//  1. In intDriver:
//     1. Examine how * (dereference) and & (address of) operators 
//        work by running the program 
//     2. Complete the short programming problems therein
//  2. Complete swap started below as specified.
//=================================================================
#include <iomanip.h>
#include <string>
#include <stdlib.h>

void swapDriver(void);
void cls(void);
void wait(void);


void intPointers(void) {
  string title("Using pointers to ints");
  cls();
  cout << setw(40+title.length()/2) << title.c_str() << "\n\n";
  int x(17), *px = &x;
  cout << "AFTER STATEMENT " << "int x(17), *px = &x;" << endl;
  cout << "x = " << x << endl;
  cout << "*px = " << *px << "\t* is the dereference operator\n";
  cout << "px = " << px << "\tpx contains address of x\n";
  cout << "&x = " << &x << "\t& is the address of operator\n\n";
  //----------------------------------------------------------
  // 1. Using px INSEAD OF x, assign -77 to x's memory location
  // YOUR CODE:

  //----------------------------------------------------------
  // 2. Using px INSEAD OF x, add 5 to value at x's memory location
  // YOUR CODE:

}


void swap(int *p, int *q) {
  // postcondition: ints to which p and q are pointing are swapped

}



int main() {
  intPointers();
  wait(); 
  swapDriver();
  wait();

  int a(0), b(4), c(10);
  // (a =  b ) = c = 7;
  a = (b = c)  = 7;
  cout << "a = " << a  << "\tb = " << b
       << "\tc = " << c << endl;


  wait();
  cout << endl;
  return 0;
} // main()



void swapDriver(void) {
  string title("Testing swap function using pointers");
  cls();
  cout << setw(40+title.length()/2) << title.c_str() << "\n\n";
  cout << "swap function prototype: void swap(int *p, int *q);\n";

  int x(5), y(2);
  cout << "BEFORE call to swap(x, y): x  = " << x
       << "\ty = " << y << endl;
  swap(&x, &y);
  cout << "AFTER call to swap(x, y):  x  = " << x
       << "\ty = " << y << endl;
}


void cls(void) {
  cout << string(55, '\n');
}


void wait (void) {
  cout << "\nPress <ENTER>...";
  cin.ignore(10, '\n');
}