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  1. import Data.List
  2.  
  3. add :: Eq a => a -> [(a, Int)] -> [(a, Int)]
  4. add x [] = [(x, 1)]
  5. add x ((y, n):rest) = if x == y
  6. 	then (y, n+1) : rest
  7. 	else (y, n) : add x rest
  8.  
  9. count :: Eq a => [a] -> [(a, Int)]
  10. count = sortBy f . foldr add [] where
  11. 	f (_, x) (_, y) = compare y x
  12.  
  13. main = print $ count "Hello"
Success #stdin #stdout 0s 6280KB
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Standard input is empty
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[('l',2),('o',1),('e',1),('H',1)]
https://ideone.com/x3tNcJ
language:
Haskell (ghc 8.4.4)
created:
11 years ago
visibility:
public

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