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  1. {-# LANGUAGE FlexibleInstances, OverlappingInstances #-}
  2.  
  3. class IsFunction a where
  4. 	isFunction :: a -> Bool
  5.  
  6. instance IsFunction (a -> b) where
  7. 	isFunction _ = True
  8.  
  9. instance IsFunction a where
  10. 	isFunction _ = False
  11.  
  12. main = print (isFunction (+)) >> print (isFunction "0")
Success #stdin #stdout 0s 6260KB
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stdin
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Standard input is empty
stdout
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True
False
https://ideone.com/d8y8q6
language:
Haskell (ghc 8.4.4)
created:
9 years ago
visibility:
secret

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