On 31-May-2005, Daniel Fischer
Am Freitag, 27. Mai 2005 02:06 schrieb Shiqi Cao:
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
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? ... To solve your problem, use import controls, for example
import Data.Set hiding (map) import qualified Data.Set as Set
will do fine.
That code only compiles with ghc 6.4, and won't compile with ghc 6.2: you'll get an error for the "hiding (map)" part, because in 6.2 Data.Set does not contain a "map" function. If you want code that compiles with both 6.2 and 6.4 and does not give any warnings with "ghc -Wall", then I think you'll need to use qualified imports, i.e. just the second line above. -- Fergus J. Henderson | "I have always known that the pursuit Galois Connections, Inc. | of excellence is a lethal habit" Phone: +1 503 626 6616 | -- the last words of T. S. Garp.