#include <iostream>
using namespace std;

/**
 * Ethan Schreiber
 * CS31
 * October 23, 2008
 *
 * This file illustrates the concept of pass by reference vs. pass by value.  
 * 
 * By default, variables are pass by value.  This means that a copy of the 
 * variable is made and passed to the function.  If you modify this variable
 * within the function, the changes will not escape the function.
 *
 * If you put an & between the parameter type and the parameter name 
 * (i.e. int &x), then the parameter is pass by reference.  This means that
 * if you modify the parameter within the function, changes will be made to
 * the variable passed into the function.
 *
 * Please see Chapter 4 (pg. 134) for a much more in depths discussion of this.
 */



void intFoo(int, int&);
void stringFoo(string, string&);


int main()
{
  // ************************************************
  // * First show pass by value/reference with ints *
  // ************************************************

  int int1 = 100;
  int int2 = 100;

  cout << endl
       << "Before Function Call" << endl
       << "   value    : "       << int1 << endl
       << "   reference: "       << int2 << endl << endl;

  // notice we don't do anything special here, we call this function
  // normally
  intFoo(int1,int2);

  cout << "After Function Call" << endl
       << "   value    : "       << int1 << endl
       << "   reference: "       << int2 << endl << endl;  

  // **************************************************
  // * Now show pass by value/reference withs strings *
  // **************************************************
  
  string string1 = string("string");
  string string2 = string("string");

  cout << endl
       << "Before Function Call" << endl
       << "   value    : "       << string1 << endl
       << "   reference: "       << string2 << endl << endl;

  // notice we don't do anything special here, we call this function
  // normally
  stringFoo(string1, string2);

  cout << "After Function Call" << endl
       << "   value    : "      << string1 << endl
       << "   reference: "      << string2 << endl << endl;    
}

/**
 * Illustrates pass by reference with ints.
 * notice the the first parameter is pass by value since
 * it has no & and the 2nd parameter is pass by reference since it
 * does have an &. 
 */
void intFoo(int firstInt, int &secondInt)
{
  firstInt  = 50;
  secondInt = 50;
}


void stringFoo(string firstString, string &secondString)
{
  firstString  = string("new string");
  secondString = string("new string");
}