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  1. data Token = Number | Operator deriving (Eq, Show)
  2.  
  3. swap :: [Token] -> [Token]
  4. swap (x:y:xs) = if x == Number && y == Operator then
  5.                   y : x : swap xs
  6.                 else 
  7.                   x : swap (y : xs)
  8. swap xs = xs
  9.  
  10.  
  11. main = putStrLn $ show $ swap [Number, Number, Number, Operator, Operator, Number, Operator, Number]
  12. -- Output: [Number,Number,Operator,Number,Operator,Operator,Number,Number]
Success #stdin #stdout 0s 4700KB
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stdin
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Standard input is empty
stdout
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[Number,Number,Operator,Number,Operator,Operator,Number,Number]
https://ideone.com/m8z8sR
language:
Haskell (ghc 8.4.4)
created:
7 years ago
visibility:
public

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