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  1. data Color = White | Blue | Red | Green | Yellow deriving (Show, Eq)
  2.  
  3. next :: Color -> [Color]
  4. next color = case color of
  5.   White -> [Blue]
  6.   Blue -> [White, Red]
  7.   Red -> [Blue, Green]
  8.   Green -> [Red, Yellow]
  9.   Yellow -> [Green]
  10.  
  11. count :: [Color] -> Int -> Int
  12. count col 1 = length col
  13. count col n = count (col >>= next) (n-1)
  14.  
  15. main = mapM_ print $ map (count [White, Blue, Red, Green, Yellow]) [1..8]
Success #stdin #stdout 0.01s 3584KB
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Standard input is empty
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5
8
14
24
42
72
126
216
https://ideone.com/5ctfo
language:
Haskell (ghc 8.4.4)
created:
13 years ago
visibility:
public

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