After working a lot with Hugs I tried to compile my Haskell code with GHC. But it does not work, I am not able to figure out how to work with the interface files (.hi). My program is build out of several modules, like this (much simpler, but facing the same problem...) File MyList.hs ============== module MyList(MkList(Empty, (:-))) where infixr 5 :- data MkList a = Empty | a :- (MkList a) deriving (Eq, Show) File ListFun.hs =============== module ListFun(mapL) where import MyList mapL f Empty = Empty mapL f (x:-xs) = f x :- mapL f xs File ListLib ============ module ListLib(module MyList, module ListFun) where import MyList import ListFun File Main.hs ============ module Main(main) where import ListLib main = putStr (show (mapL (+1) (1:-2:-Empty))) As I said the code works with hugs, and I want to have the hierarchy in the library structure. So, how do I compile this in GHC? I hoped, that it would be enough to compile all files with the -c option (generating .hi and .o files) and then compiling Main.hs to get an executable program. Howeve, I get the following:
ghc Main.hs ghc: module version unchanged at 7 Undefined first referenced symbol in file MyList_ZCzm_con_info Main.o MyList_zdfShowMkList_closure Main.o ListFun_mapL_closure Main.o MyList_Empty_static_closure Main.o ld: fatal: Symbol referencing errors. No output written to a.out
So, what's wrong, and am I totally on the wrong track... (I studied the GHC User Guide, but could not find the answer to my problem). Thanks in advance! Ingo Sander