Haskell Cookbook

How to do it...

1. Open src/Main.hs; we will implement merge sort here.
2. We will start with the implementation of two utility functions; group2 and merge.
3. The group2 function is used to divide the input list in pairs. We will ensure that the pairs are sorted in the result. A single element is considered sorted:

        -- Group elements in groups of twos, but when we group it we         keep        them        -- sorted.         group2 :: Ord a => [a] -> [[a]]        group2 [] = []        -- A single element is already sorted.        group2 (x:[]) = [[x]]        -- Create groups of two and sort them        group2 (x:y:xs) = (sortPair x y) : group2 xs        where         sortPair x y | x >= y    = y : x : []                 | otherwise = x : y : []

4. The merge function is used to merge two input lists. It is assumed that the input lists are already ...