Ellipses Operator (. . .)

This operator is used to represent various number of parameters involve. This is mainly used in function arguments , when the number of arguments is not known.

Ex -
int foo(int i, int j, . . .);

But we can use ellipses operator in other part of coding also.

In switch case

main()
{
       --------
       --------
       switch(3)
       {
               case 1 ... 4:
                    printf("Option is between 1 to 4);
                    break;

               case 5 ... 9:

                    printf("Option is between 5 to 9);

                    break;

        }

}

In array

Ellipses operator used in array initialization also. Using this operator we can partially initialize our arrays.

Ex - 

main()

{

         int arr[] = { [0 ... 4] 4, [5 ... 9] 5};

         printf("arr[0] %d\n", arr[0]);

         printf("arr[6] %d\n", arr[6]);

}

o/p - 

arr[0] 4

arr[6] 5

Partially initialize the array 

main()

{

        int arr[10] = { [3]5, [1] = 4, [4] 3, [0] = 0 };

         printf("arr[0] %d\n", arr[0]);

         printf("arr[3] %d\n", arr[3]);

         printf("arr[4] %d\n", arr[4]);

}

o/p - 

arr[0] 0

arr[3] 5

arr[4] 3