[Haskell-cafe] ghc 6.4 import problem

Henning Thielemann lemming at henning-thielemann.de
Tue May 31 06:29:01 EDT 2005

On Thu, 26 May 2005, Shiqi Cao wrote:

> Hi,
> I tried to port some code from ghc 6.2 to ghc 6.4, but I got the
> following error
> PrelExts.lhs:41:25:
>     Ambiguous occurrence `map'
>     It could refer to either `GHC.Base.map', imported from Data.List at
> PrelExts.lhs:11:0-15
>                           or `Data.Set.map', imported from Data.Set at
> PrelExts.lhs:10:0-14

This means that there is a 'map' for lists (Data.List.map) and one for
sets (Data.Set). You should import them qualified.

> The following is the first part of the code
> module PrelExts where
> import Data.FiniteMap
> import Data.Set
> import Data.List
> import IO
> There is no problem under ghc 6.2. What should I do?

import qualified Data.Set  as Set
import qualified Data.List as List

and call Set.map and List.map

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