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  1. main = do
  2.   print $ safeHead ([] :: [Int])
  3.   print $ safeHead ([1,2] :: [Int])
  4.  
  5. safeHead :: [a] -> Maybe a
  6. safeHead = partial head (not . null)
  7.  
  8. partial :: (a -> b) -> (a -> Bool) -> a -> Maybe b
  9. partial f p x | p x = Just $ f x | otherwise = Nothing
  10.  
Success #stdin #stdout 0.02s 3580KB
comments (?)
stdin
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Standard input is empty
stdout
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Nothing
Just 1
https://ideone.com/pF44q
language:
Haskell (ghc 8.4.4)
created:
12 years ago
visibility:
public

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