Re: [Haskell-cafe] Non-derivable Typeable
Won't it derive it with StandaloneDeriving? Cheers, Pedro On Tue, Jan 22, 2013 at 1:28 PM, Roman Cheplyaka r...@ro-che.info wrote: I need to declare a Typeable instance for a type which has an argument of kind * - *. GHC refuses to derive it. What is a recommended way to go about it? In particular, if I write the instance by hand, how important is the fingerprint, and how could I generate it? Roman ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Non-derivable Typeable
It doesn't seem to — am I doing something wrong? GHCi, version 7.6.1.20121207: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer-gmp ... linking ... done. Loading package base ... linking ... done. Prelude :set -XDeriveDataTypeable -XStandaloneDeriving Prelude :m +Data.Typeable Prelude Data.Typeable data Foo m = Foo (m ()) Prelude Data.Typeable deriving instance Typeable1 m = Typeable (Foo m) interactive:5:1: Can't make a derived instance of `Typeable (Foo m)': `Foo' must only have arguments of kind `*' In the stand-alone deriving instance for `Typeable1 m = Typeable (Foo m)' Roman * José Pedro Magalhães j...@cs.uu.nl [2013-01-22 13:36:26+] Won't it derive it with StandaloneDeriving? Cheers, Pedro On Tue, Jan 22, 2013 at 1:28 PM, Roman Cheplyaka r...@ro-che.info wrote: I need to declare a Typeable instance for a type which has an argument of kind * - *. GHC refuses to derive it. What is a recommended way to go about it? In particular, if I write the instance by hand, how important is the fingerprint, and how could I generate it? Roman ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Non-derivable Typeable
I just found mkTyCon3 which generates the fingerprint automatically. (I was looking at Data.Typeable.Internal.mkTyCon before.) That answers my question. (Of course, a way to derive the instance would be even better...) Roman * Roman Cheplyaka r...@ro-che.info [2013-01-22 15:28:55+0200] I need to declare a Typeable instance for a type which has an argument of kind * - *. GHC refuses to derive it. What is a recommended way to go about it? In particular, if I write the instance by hand, how important is the fingerprint, and how could I generate it? Roman ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Non-derivable Typeable
Yes, that will work. But soon we'll have poly-kinded Typeable in HEAD, which will be able to derive that instance. Cheers, Pedro On Tue, Jan 22, 2013 at 2:34 PM, Roman Cheplyaka r...@ro-che.info wrote: I just found mkTyCon3 which generates the fingerprint automatically. (I was looking at Data.Typeable.Internal.mkTyCon before.) That answers my question. (Of course, a way to derive the instance would be even better...) Roman * Roman Cheplyaka r...@ro-che.info [2013-01-22 15:28:55+0200] I need to declare a Typeable instance for a type which has an argument of kind * - *. GHC refuses to derive it. What is a recommended way to go about it? In particular, if I write the instance by hand, how important is the fingerprint, and how could I generate it? Roman ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Non-derivable Typeable
Thanks, looking forward to it! Roman * José Pedro Magalhães j...@cs.uu.nl [2013-01-22 14:41:25+] Yes, that will work. But soon we'll have poly-kinded Typeable in HEAD, which will be able to derive that instance. Cheers, Pedro On Tue, Jan 22, 2013 at 2:34 PM, Roman Cheplyaka r...@ro-che.info wrote: I just found mkTyCon3 which generates the fingerprint automatically. (I was looking at Data.Typeable.Internal.mkTyCon before.) That answers my question. (Of course, a way to derive the instance would be even better...) Roman * Roman Cheplyaka r...@ro-che.info [2013-01-22 15:28:55+0200] I need to declare a Typeable instance for a type which has an argument of kind * - *. GHC refuses to derive it. What is a recommended way to go about it? In particular, if I write the instance by hand, how important is the fingerprint, and how could I generate it? Roman ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
