hi-boot files can't contain class declarations. This should be checked, but isn't, hence puzzling message. GHC 6.4 has a better setup. Actually, it still doesn't check for absence of class decls, but it will shortly. Simon | -----Original Message----- | From: haskell-cafe-bounces@haskell.org [mailto:haskell-cafe-bounces@haskell.org] On Behalf Of | Henning Thielemann | Sent: 04 May 2005 10:10 | To: Haskell Cafe | Subject: [Haskell-cafe] Mutual recursive modules with GHC: Classes, instances | | | I tried to set up mutual recursive modules according to section 4.6.10. of | the manual of GHC-6.2.2. I illustrate my problems with a simple fictitious | example. | | ---- A.hi-boot ---- | | module A where | | | class GHC.Num.Num a => C a where | answer :: a | | f :: B.T -> GHC.Num.Int | | | ---- A.hs ---- | | module A where | | import B | | class Num a => C a where | answer :: a | | instance C Int where | answer = 42 | | f :: B.T -> Int | f (B.Cons x) = x | | | ---- B.hs ---- | | module B where | | import {-# SOURCE #-} A | | | data T = Cons Int | | newAnswer :: Int | newAnswer = A.answer + 1 | | -------------- | | | $ ghc --make A.hs B.hs | Chasing modules from: A.hs,B.hs | Compiling B ( B.hs, B.o ) | | B.hs:1: | Failed to find interface decl for `A.$dmanswer' | from module `A' | _______________________________________________ | Haskell-Cafe mailing list | Haskell-Cafe@haskell.org | http://www.haskell.org/mailman/listinfo/haskell-cafe