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"LANGUAGE" pragma seems to have no effect on the editor feedback.

Farhad Mehta

December 10, 2018 13:21

Answered

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Hi,

Maybe this is expected behaviour (and I have not understood something), but I notice that the following code does not give me any errors or warnings in the editor, but (as expected) does not build or run:

----

{-# LANGUAGE MonomorphismRestriction #-}
module Main
where

import System.IO

-- concat'' :: [[a]] -> [a]
concat'' = foldr (++) []

main = do
putChar 'x'

----

Thanks,
Farhad

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1 comment

• 
  Manuel Chakravarty December 15, 2018 20:51 Official comment

  Thanks for the report.

  Haskell for Mac deactivates the monomorphism restriction for interactive evaluation (just like GHCi); however, it also applies this to modules it loads, not just the playground. I should probably change that.

  Nevertheless, generally, the LANGUAGE pragma ought to work just fine. (I often use it myself.)

   

  Thanks, Manuel