Ambiguous Occurrence

Question

I am currently learning how to write type classes. I can\'t seem to write the Ord type class with compile errors of ambiguous occurrence.

module Practice where

         


        

Answer 1

hammar is right, it's because of clashing with standard Prelude names. But there are another solutions in addition to hiding names from Prelude.

You can import Prelude qualified:

module Practice where

import qualified Prelude as P

...

Next, you can gain access to both you and standard version of function: max will execute your version, and P.max will execute standard Prelude's.

There is also way to completely hide all standard Prelude functions: GHC's extension NoImplicitPrelude (http://www.haskell.org/haskellwiki/No_import_of_Prelude). It can be activated writing

{-# LANGUAGE NoImplicitPrelude #-}

in the very beginning of your file