Sorting a list

In this recipe, we will write a pseudo-quick sort using recursion. We call it pseudo-quick sort because it looks deceptively such as quick sort, but does not have a performance anywhere near it. 

Getting ready

Use Stack to create a new project, pseudo-qsort, with the simple template and build it, after changing directory to the project folder:

      > stack new pseudo-qsort simple
      > stack build

How to do it...

1. Open src/Main.hs and write the qsort implementation. The qsort involves the following:
   • Choosing an element of the list to be sorted
   • Using the chosen element as a pivot, divide the input list into two parts:
     • Subset of the list smaller than the pivot element
     • Subset of the list greater than or equal to the pivot element
   • Recursively sorting two parts in a similar way
2.  In Haskell, we can implement a method like quick sort quite easily. Ord a in the qsort declaration signifies that the elements of the list [a] can be compared for inequality, and it is possible to use the...