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  1. (?) p = \x -> if p x then Left x else Right x
  2. p --> (f,g) = either f g . (p?)
  3. (!) x = \_ -> x
  4.  
  5. maybeHead = null --> ((Nothing!), Just . head)
  6.  
  7. main = do print $ maybeHead ([]::[Int])
  8.           print $ maybeHead [1,2]
Success #stdin #stdout 0s 6224KB
comments (?)
stdin 
Standard input is empty
stdout 
Nothing
Just 1
https://ideone.com/NlgFig
language:
Haskell (ghc 8.4.4)
created:
9 years ago
visibility:
public

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