How to pass or declare array members in c?

Question

I developed a program that is supposed to pass the following members of the array of double purchase from the following function:

float beverages ()
{              
   char response;
   double purchase [8]= {3.50, 3.80, 3.90, 4.20, 4.00, 4.30, 3.00, 3.10};
   printf("\nEnter your order: ");
   scanf("%c", response);

   if (response == 'l')
   {
      purchase [0];
      printf("You have chosen a Regular Long Black coffee\n");
      printf("that will be %.2f dollars", purchase [0]); 

   }
   else if (response == 'L')
   {
      purchase [1];
      printf("You have chosen a Large Long Black coffee\n");
      printf("that will be %.2f dollars", purchase [1]);

   }
   else if (response == 'f')
   {
      purchase [2];
      printf("You have chosen a Regular Flat White coffee\n");
      printf("that will be %.2f dollars", purchase [2]); 

   }
   else if (response == 'F')
   {
      purchase [3];
      printf ("You have chosen a Large Flat White coffee\n");
      printf("that will be %.2f dollars", purchase [3]); 

   }

   else if (response == 'c')
   {
      purchase [4];
      printf("You have chosen a Regular Cappuccino\n");
      printf("that will be %.2f dollars", purchase [4]);    
   }
   else if (response == 'C')
   {
      purchase [5];
      printf("You have chosen a Large Cappuccino\n");
      printf("that will be %.2f dollars", purchase [5]);        
   }
   else if (response == 't')
   {
      purchase [6];
      printf("You have chosen a Regular Tea\n");
      printf("that will be %.2f dollars", purchase [6]);    
   }
   else  if (response == 'T')
   {
      purchase [7];
      printf("You have chosen a Large Tea\n");
      printf("that will be %.2f dollars", purchase [7]);    
   }

   return purchase[];
}   

and I have it in the int main like:

int main()
{
  ...
  printf("MENU!");
  decision (choice);
  purchase [] = beverages();
  ...
  return 0;
}  

with the following code purchase [] = beverages(); there seems to be a problem where the compiler is saying that purchase is undeclared and there is and unexpected expression before the ] token (by the way the errors are only within the int main). It seems that maybe I have not passed the array from the function properly or something? I've tried adding the value 8 e.g purchase[8] = beverages(); but then the compiler says that purchase is not a pointer or an array. How do I debug this? Am I simply not using right syntax or am I not passing the array correctly?

Answer 1

As 'beverages()' function is want to return double array then you need to modify like

  double * beverages()
     {        
        static double purchase [8]= {3.50, 3.80, 3.90, 4.20, 4.00, 4.30, 3.00, 3.10};
        // Line of code
        return purchase;
     }

In main function you need to modify like

main()
{
   double *purchase = beverages();     
}

Variable purchase defined in beverages() is local to that function you can not access it in main()

Answer 2

The lexical scope of the array purchase is within procedure beverages. Instead of trying to access the array outside in main, you can declare it inside main.

int main(void) 
{
      double purchase [8]= {3.50, 3.80, 3.90, 4.20, 4.00, 4.30, 3.00, 3.10};
      ... 
      ...
}

Now you can pass the address of the array via pointer to the procedure beverages

void beverages(double *purchase) {

    char response;
    printf("\nEnter your order: ");
    scanf("%c", &response);

    if (response == 'l')
    {
        printf("You have chosen a Regular Long Black coffee\n");
        printf("that will be %.2f dollars", *purchase + 0);

    }
    ...

}

And call the procedure inside main

int main(void)
{

      double purchase [8]= {3.50, 3.80, 3.90, 4.20, 4.00, 4.30, 3.00, 3.10};
;

      beverages(purchase);


}

Also if you want to change the value of the array

*(purchase + i) = value  // where i is index location