Migrating function from LET to WHERE in Haskell

haskell

Solution

You need to match the indentation of the expressions in a `where` clause, e.g.

quicksort :: (Ord a) => [a] -> [a]  
quicksort [] = []  
quicksort (x:xs) = smallerSorted ++ [x] ++ biggerSorted 
    where smallerSorted = quicksort [a | a <- xs, a <= x]  
          biggerSorted = quicksort [a | a <- xs, a > x]

or

quicksort :: (Ord a) => [a] -> [a]  
quicksort [] = []  
quicksort (x:xs) = smallerSorted ++ [x] ++ biggerSorted 
    where
        smallerSorted = quicksort [a | a <- xs, a <= x]  
        biggerSorted = quicksort [a | a <- xs, a > x]

Problem

In order to improve my Haskell skills I decided to go through some example code and try to rewrite in a different way. Here is the initial function: ``` quicksort :: (Ord a) => [a] -> [a] quicksort [] = [] quicksort (x:xs) = let smallerSorted = quicksort [a | a <- xs, a <= x] biggerSorted = quicksort [a | a <- xs, a > x] in smallerSorted ++ [x] ++ biggerSorted ``` Here is the migrated function: ``` quicksort :: (Ord a) => [a] -> [a] quicksort [] = [] quicksort (x:xs) = smallerSorted ++ [x] ++ biggerSorted where smallerSorted = quicksort [a | a <- xs, a <= x] biggerSorted = quicksort [a | a <- xs, a > x] ``` However looks to me that it is not working. Is there something wrong? Can functions using LET ported to WHERE? This is my error output: ``` /Users/graph/Documents/Uni/Haskell/hey.hs:43:5: parse error on input `biggerSorted' Failed, modules loaded: none. ``` Many thanks!

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