haskellhaskell-platform

I got "Not in scope SortOn" error message

Even after I imported the Data.List package, I still get "Not in scope: sortOn" error message. I am using HaskellPlatform 2014.2.0 version.

Solution

  • this Error message is there because sortOn has been introduced in base-4.8 (see hackage-base but haskell-platform 2014.2.0 only includes base-4.7.0.1 (see haskell-platform-doc)

    but you can easily build it on your own with sortBy (see @vikingsteve's answer) compare and on (you need to import Data.List for that)