in Standard ML only and provide coments

1. Write a quicksort function of type int list -> int list. Quicksort works very similar to the mergesort but instead of halving lists the lists are split according to a pivot element. Here is a review of the quicksort algorithm:

   • First pick an element on the input list and call it the pivot (the first element of the list is usually a good choice).

   • Partition the rest of the list into two sublists: one with all the elements less than the pivot and one with all the elements not less than the pivot.

   • Recursively sort the sublists.

   • Combine the sorted sublists and the pivot into the final sorted list.

You have to use pattern matching in your function definition.