(I forgot to say, this was with 6.4.2.) Another problem I'm having is that when I consume a datatype, its derived instances aren't available; and even in an hs-boot file, a 'deriving' clause is illegal on a type with no constructors. So I can't compile B in this case: module A where import B data DT1 = X | Y deriving Show module B where import {-# SOURCE #-} A data DT2 = MkDT2 { Q :: DT1 } deriving Show Because of missing Show instances for DT1. (In practise, I think it might work if I spell out the full declaration of DT1 with the deriving clause, but I don't want the creep: X and Y are really records entailing additional types B need not concern itself with.) I'm hoping 6.6 will allow me to say this in the hs-boot file: data DT1 deriving Show On Fri, Aug 11, 2006 at 10:59:29AM +0100, Simon Peyton-Jones wrote:

Well this is odd. The manual (for 6.6 anyway) says that class decls are allowed in hs-boot files, but instance decls are not, whereas the code seems to say that class decls aren't but instance decls are!

I will look into this. Meanwhile, I'm afraid you just can't put a class decl in the hs-boot file with the version of the compiler you have.

Simon

| -----Original Message----- | From: glasgow-haskell-users-bounces@haskell.org [mailto:glasgow-haskell-users-bounces@haskell.org] | On Behalf Of Gaal Yahas | Sent: 09 August 2006 18:25 | To: GHC Users Mailing List | Subject: class declaration in boot file | | I'm trying to solve a circularity problem with .hs-boot, but am getting | the error: "Illegal class declaration in hs-boot file". | | The offending declaration is: | | class (Monad m, Functor m, Eq a, Data a, Typeable a) => ICoercible m a | a -> m | | I've tried with and without the fundeps. Data and Typeable are in scope, | and -fglasgow-exts is set. Any ideas on what else I should be doing? | | -- | Gaal Yahas | http://gaal.livejournal.com/ | _______________________________________________ | Glasgow-haskell-users mailing list | Glasgow-haskell-users@haskell.org | http://www.haskell.org/mailman/listinfo/glasgow-haskell-users

-- Gaal Yahas http://gaal.livejournal.com/

Prodded by your mail, I've gotten back to hs-boot files. I've fixed the HEAD so that both class and instance declarations are allowed in hs-boot files. But not 'deriving'! Simon | -----Original Message----- | From: Gaal Yahas [mailto:gaal@forum2.org] | Sent: 11 August 2006 21:06 | To: Simon Peyton-Jones | Cc: GHC Users Mailing List | Subject: Re: class declaration in boot file | | (I forgot to say, this was with 6.4.2.) | | Another problem I'm having is that when I consume a datatype, its | derived instances aren't available; and even in an hs-boot file, a | 'deriving' clause is illegal on a type with no constructors. So I can't | compile B in this case: | | module A where | | import B | data DT1 = X | Y deriving Show | | module B where | | import {-# SOURCE #-} A | | data DT2 = MkDT2 { Q :: DT1 } deriving Show | | Because of missing Show instances for DT1. (In practise, I think it | might work if I spell out the full declaration of DT1 with the deriving | clause, but I don't want the creep: X and Y are really records entailing | additional types B need not concern itself with.) | | I'm hoping 6.6 will allow me to say this in the hs-boot file: | | data DT1 deriving Show | | On Fri, Aug 11, 2006 at 10:59:29AM +0100, Simon Peyton-Jones wrote: | > Well this is odd. The manual (for 6.6 anyway) says that class decls are | > allowed in hs-boot files, but instance decls are not, whereas the code | > seems to say that class decls aren't but instance decls are! | > | > I will look into this. Meanwhile, I'm afraid you just can't put a class | > decl in the hs-boot file with the version of the compiler you have. | > | > Simon | > | > | -----Original Message----- | > | From: glasgow-haskell-users-bounces@haskell.org | > [mailto:glasgow-haskell-users-bounces@haskell.org] | > | On Behalf Of Gaal Yahas | > | Sent: 09 August 2006 18:25 | > | To: GHC Users Mailing List | > | Subject: class declaration in boot file | > | | > | I'm trying to solve a circularity problem with .hs-boot, but am | > getting | > | the error: "Illegal class declaration in hs-boot file". | > | | > | The offending declaration is: | > | | > | class (Monad m, Functor m, Eq a, Data a, Typeable a) => ICoercible m a | > | a -> m | > | | > | I've tried with and without the fundeps. Data and Typeable are in | > scope, | > | and -fglasgow-exts is set. Any ideas on what else I should be doing? | > | | > | -- | > | Gaal Yahas | > | http://gaal.livejournal.com/ | > | _______________________________________________ | > | Glasgow-haskell-users mailing list | > | Glasgow-haskell-users@haskell.org | > | http://www.haskell.org/mailman/listinfo/glasgow-haskell-users | | -- | Gaal Yahas | http://gaal.livejournal.com/