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    <p>I've broken this down into steps that should make this easier to grasp. First, sort the list, then reduce it into a list of (Word, Count) tuples.</p> <pre><code>import Data.Char (toLower) quicksort :: (Ord a) =&gt; [a] -&gt; [a] quicksort [] = [] quicksort (x:xs) = (quicksort [a|a&lt;-xs, a&lt;=x]) ++ [x] ++ (quicksort [a|a&lt;-xs, a&gt;x]) addCount :: String -&gt; [(String, Int)] -&gt; [(String, Int)] addCount a [] = [(a, 1)] addCount a (x:xs) | a == fst x = (fst x, (snd x) + 1) : xs | otherwise = x : (addCount a xs) occurrences :: [(String, Int)] -&gt; [String] -&gt; [(String, Int)] occurrences counts [] = counts occurrences counts (x:xs) = occurrences countL xs where countL = addCount x counts myList = ["AAA","America", "England", "Spain","Ireland", "aeroplane", "aeroplane", "Aeroplane", "AeRoPlAne", "helicopter", "HELICOPTER", "Zebra", "America", "Elephant", "abc", "A.B.C." , "haskell", "Haskell", "ZZZ", "zzz"] main = do let downcased = map (map toLower) myList let sorted = quicksort downcased let occurencesL = occurrences [] sorted putStrLn . show $ occurencesL putStrLn . show $ [head occurencesL, last occurencesL] </code></pre> <p>This is <em>very</em> verbose but, I'm hoping you have an easier time understanding what is happening this way.</p> <p>An example of a shorter way:</p> <pre><code> import Data.Char (toLower) import Data.List main = do let l = map (\a -&gt; (head a, length a)) $ groupBy (\x y -&gt; (map toLower x) == (map toLower y)) myList putStrLn . show $ l putStrLn . show $ [head l, last l] </code></pre>
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    1. POQuicksort a list and convert it into list of tuples (elem, count)
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    1. POQuicksort a list and convert it into list of tuples (elem, count)
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    1. COGreat thanks for your input. I am a haskell beginner and going through learn-you-a-haskell. Don't know how to run main? Please guide. I ran quicksort and it works but the result for occurrence part don't know how to get it?
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    2. COYou should put this in a file ending in 'hs', say "Sort.hs". The easiest way to run a single file is to use the 'runghc' or 'runhaskell' commands eg. `runghc Sort.hs` on my Mac. This is the same on Linux but, I'm unsure about Windows. You can also run it from GHCI; load the file with ':l Sort' the run 'main'.
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    3. COI definitely will like to see the most concise code. I don't find any difficulty in reading and understanding the code so far. My problem was I was getting parse error due to some indentation issue in my code or and editor tool issue or something (weird).
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