/*  Name        Description
**  -------     -------------------------------------------------------
**  funcptr.c   This small C program shows how program flow
**              can be controlled by function pointers.
**
**              This example program was brought to you by
**              Scott Wenger, Box 802, Stevens Point, WI 54481, USA
**              panther@wctc.net
**              http://www.private-files.com/sware.html
**        
**              In the example below, you will see that an array
**              of function pointers is declared.  Allowing 
**              the user to move forward or backward through that 
**              array controls program flow.
**
**              Naturally, many more functions can be used but
**              this example gives you the outline.  
**
**              This code compiles, links, and executes properly.  
**              Check your specific implementation of getch, if necessary
*/
 
#include <stdio.h>
#include <stdlib.h>
#include <conio.h>     // for getch()

 
#define NUMB_FUNCTIONS 5  // number of functions
 
// function prototypes 
int f1(), f2(), f3(), f4(), f5();
void title();
void prompt(int i);
void clr_scr();
void s_line();

main()
{
  // declare func as an array of function pointers
  // and initilize the array with the function ptrs.
  static int (*func[])() = { f1, f2, f3, f4, f5 }; 
  int retval;
  int active = 1;
  int i = -1;    
  int ch;
  
  // Functions can be traversed, forward or backward
  // through an array of pointers to functions as shown below.
  // In this example, the user controls the direction of program flow.
  clr_scr();
  title();
  
  while (active)  { 
    prompt(i);  	  
    ch = getch();  // get direction from user (forward or backward)	  
    
    if (ch == 'x' || ch == 'X') break;

    // Check valid range	    
    if (i >= -1 && i < NUMB_FUNCTIONS - 1 && (ch == 'f' || ch == 'F') ) i++;
    else if (i > 0 && i < NUMB_FUNCTIONS && (ch == 'b' || ch == 'B') ) i--;    
        
    retval = ( *(func[i]) )();   // call the functions
  }  
  exit(0);
} 



int f1()
{
  // this function does whatever you want
  printf("\n>>>>> i is 0, so *(func[i]))() gets us inside function #1\n\n\n");	
  s_line();
  return(1);
}


int f2()
{
  // this function does whatever you want
  printf("\n>>>>> i was 1, so *(func[i]))() gets us inside function #2 \n\n\n");	
  s_line();
  return(1);  
}


int f3()
{
  // this function does whatever you want
  printf("\n>>>>> i was 2, so *(func[i]) )() gets us inside function #3 \n\n\n");	
  s_line();
  return(1);
}


int f4()
{
  // this function does whatever you want
  printf("\n>>>>> i was 3, so *(func[i]))() gets us inside function #4 \n\n\n");	
  s_line();
  return(1);
}


int f5()
{
  // this function does whatever you want
  printf("\n>>>>> i was 4, so *(func[i]) )() gets us inside function #5 \n\n\n");	
  s_line();
  return(1);
}


void prompt(int i)
{
  if (i == -1 || i == 0) 
    printf("Press 'f' to move forward or 'x' to quit\n");
  if (i == NUMB_FUNCTIONS - 1)   
    printf("Press 'b' to move backward or 'x' to quit\n");
  if (i > 0 && i < NUMB_FUNCTIONS - 1) 
    printf("Press 'f' for forward, 'b' for backward, or 'x' to quit\n");
}	    


void title()
{
  printf("\n\n");
  printf("   ********************************************************************\n\n");	
  printf("      This example (funcptr.c) uses an array of function pointers      \n");
  printf("      to control program flow.                                         \n");
  printf("                                                                       \n");
  printf("      The array of function pointers was declared as follows:          \n");
  printf("      static int (*func[])() = { f1, f2, f3, f4, f5 };                 \n"); 
  printf("                                                                       \n");
  printf("      This example uses the variable 'i' as an index into the array.   \n");
  printf("      Remember that, in C, arrays are 0-based.                         \n\n");
  printf("   ********************************************************************\n");
  printf("\n\n\n\n\n");
}

void s_line()
{
  register int z;
  for (z = 0; z < 75; z++) printf("-");
  printf("\n\n");
}


void clr_scr()
{
  register int z;
  for (z = 0; z < 80; z++) printf("\n");
}