/*
 *  =====================================================================
 *  Demonstrate use of "call by value" mechanism in function calls.
 *
 *  Copyright (C) 1994-96 by Mark Austin and David Mazzoni.
 *                                                                     
 *  This software is provided "as is" without express or implied warranty.
 *  Permission is granted to use this software on any computer system,
 *  and to redistribute it freely, subject to the following restrictions:
 * 
 *  1. The authors are not responsible for the consequences of use of
 *     this software, even if they arise from defects in the software.
 *  2. The origin of this software must not be misrepresented, either
 *     by explicit claim or by omission.
 *  3. Altered versions must be plainly marked as such, and must not
 *     be misrepresented as being the original software.
 *  4. This notice is to remain intact.
 *                                                                     
 *  Written By : D. Mazzoni and M. Austin                    January 1994
 *  =====================================================================
 */

#include <stdio.h>

int main( void ) {
int iVal  = 4, iReturnVal;
int iVal1 = 1,  iVal2 = 2;

/* function prototypes */

int tryChange(int iVal);
void changeTwoVars(int * ipVal1, int * ipVal2);

  /* [a] : Pass value of iVal */

     printf("In main() : Passing value of iVal to \"tryChange\"\n" );
     iReturnVal = tryChange(iVal);                      /* try to change iVal           */
     printf("In main() : Now iVal = %i   iReturnVal = %i", iVal,iReturnVal); /* "iVal = 4
                                      		        iReturnVal = 37" is printed */
  /* [b] : Now pass references to variables */

     printf("\nIn main() : Passing references to the function \"changeTwoVars\"\n" );
     changeTwoVars( &iVal1, &iVal2 );
     printf("In main() : Now  iVal1 = %i  iVal2 = %i\n", iVal1, iVal2 );
}

tryChange(int iPassed) {
enum{ AddVal = 103 };

  /* [a] : Change a parameter that was passed by value */

     printf("In tryChange() : iPassed = %i\n", iPassed); 
     printf("In tryChange() : Adding %i to iPassed...\n", AddVal );
     iPassed += AddVal;
     printf("In tryChange() : Now iPassed = %i\n", iPassed); 

     return iPassed;
}

void
changeTwoVars( int * ipFirst, int * ipSecond ) {
enum{ Mult1 = 2, Mult2 = 10 };

  /* [a] : Change two variables where a reference value has been passed */

     printf("In changeTwoVars() : *ipFirst = %i *ipSecond = %i\n", *ipFirst, *ipSecond);  
     printf("In changeTwoVars() : Multiplying arguments by %i and %d, respectively...\n",
            Mult1, Mult2 );

     *ipFirst *= Mult1; 
     *ipSecond *= Mult2;

     printf("In changeTwoVars() : Now *ipFirst = %i *ipSecond = %i\n", *ipFirst, *ipSecond);  
}