/* C - Calculator Revised.  */
/* Bstruct -> 09/01/2008 .  */

#include <stdio.h>
#include <stdlib.h>

/*******Math Functions*******/
float addition(float a,float b);
float (*a)(float a,float b);           /* Pointer Declaration */

float subtraction(float a,float b);
float (*s)(float a,float b);           /* Pointer Declaration */

float multiplication(float a,float b);
float (*m)(float a,float b);           /* Pointer Declaration */

float division(float a,float b);
float (*d)(float a,float b);           /* Pointer Declaration */

int user_menu(void);

/*Variables to hold user - input*/
float nr_1,nr_2;

main()
{
      puts("\t\t##############");
      puts("\t\t###[C-CALC]###");
      puts("\t\t##############");
      printf("\n\n\n");
      
      a = addition;                 /* Initializing Pointer to Function */
      s = subtraction;              /* Initializing Pointer to Function */
      m = multiplication;           /* Initializing Pointer to Function */
      d = division;                 /* Initializing Pointer to Function */
      
      /* Now to get the input from user*/
      
      printf("Enter any two real values to be calculated...\n");
      printf("Hit [RETURN] when done:\n\n\n");
      
      printf("1st Number:\n");
      scanf("%f", &nr_1);
      
      /* Check that user didn't enter a NULL */
      if (nr_1 == 0)
      {
               printf("\n\aYou can't enter a NULL, program will re-start...\n");
               return (main());
               }
               
      printf("2nd Number:\n");
      scanf("%f", &nr_2);
      
      /* Check that user didn't enter a NULL */
      if (nr_2 == 0)
      {
               printf("\n\aYou can't enter a NULL, program will re-start...\n");
               return (main());
               }
while(1)
{
        puts("\n\n\nChoose your calculation method...");
        
switch(user_menu())
{
case 1:
{
     printf("\n%.2f + %.2f = %.2f", nr_1,nr_2,a(nr_1,nr_2));
     break;
}
case 2:
{
     if (nr_1 > nr_2)
     {
              printf("\n%.2f - %.2f = %.2f", nr_1,nr_2,s(nr_1,nr_2));
              }
     if (nr_2 > nr_1)
     {
              printf("\n%.2f - %.2f = %.2f", nr_2,nr_1,s(nr_1,nr_2));
              }
              break;
}
case 3:
{
              printf("\n%.2f X %.2f = %.2f", nr_1,nr_2,m(nr_1,nr_2));
              
              break;
}     
case 4:
{
     if (nr_1 > nr_2)
     {
              printf("\n%.2f / %.2f = %.3f", nr_1,nr_2,d(nr_1,nr_2));
              }
     if (nr_2 > nr_1)
     {
              printf("\n%.2f / %.2f = %.3f", nr_2,nr_1,d(nr_1,nr_2));
              }
              break;
}
default:
        {
              printf("\n\nIncorrect Choice, Please Re-Enter...\n");
              }          
case 5:
{
     printf("\n\a\n\nReturning to main menu...\n");
     return(main());
     }
case 6:
{
     printf("\n\nExiting now...\n");
     exit(EXIT_SUCCESS);
     }  

}      /*Closing Switch*/
}      /*Closing While */
}      /*Closing Main()*/  
        
/*****Addition Function******/
float addition(float nr_1,float nr_2)
{
     return (nr_1 + nr_2);
}
/*****Subtraction Function***/ 
float subtraction(float nr_1,float nr_2)
{
      if (nr_1 > nr_2)
      {
            return (nr_1 - nr_2);
            }
            else
            return (nr_2 - nr_1);
}
/***Multiplication Function**/
float multiplication(float nr_1,float nr_2)
{
      return ((nr_1)*(nr_2));
}
/*****Division Function******/
float division(float nr_1,float nr_2)
{
      if (nr_1 > nr_2)
      {
            return (nr_1 / nr_2);
            }
            else
            return (nr_2 / nr_1);
}      
/*********User Menu**********/
int user_menu(void)
{
    int selection_1;
    
    puts("1         -         Addition");
    puts("2         -         Subtraction");
    puts("3         -         Multiplication");
    puts("4         -         Division");
    printf("\n");
    puts("5        -          Re - Start");
    puts("6        -          Exit");
    
    scanf("%d", &selection_1);
    
    return selection_1;
}