Hi,
that's a bug in GHC---it erroneously accepts polymorphic instances which
violate the FD of a class.
-Iavor
On Fri, Mar 18, 2011 at 7:08 AM, Daniel Fischer <
daniel.is.fisc...@googlemail.com> wrote:
> On Friday 18 March 2011 14:40:40, JP Moresmau wrote:
> > Thanks to you all, I think I underst
On Friday 18 March 2011 14:40:40, JP Moresmau wrote:
> Thanks to you all, I think I understand better.
> instance Search Id Id where
> search _ _ i = only (FoundId i)
>
> Is too restrictive on the first type, so declaring instead:
> instance Search id Id where
> search _ _ i = only (FoundId i)
Thanks to you all, I think I understand better.
instance Search Id Id where
search _ _ i = only (FoundId i)
Is too restrictive on the first type, so declaring instead:
instance Search id Id where
search _ _ i = only (FoundId i)
Fixed the issue!! Now the initial "id" is not Id and everybody is
On Friday 18 March 2011 13:35:22, JP Moresmau wrote:
> These are GHC types, but here is a self-contained example:
> {-# LANGUAGE MultiParamTypeClasses, FunctionalDependencies,
> FlexibleInstances #-}
>
> data Id=Id String
>
> data Result id =ResultId Id
> | ResultGen id
>
> data Sig id=IdSig
On Fri, Mar 18, 2011 at 13:35, JP Moresmau wrote:
> These are GHC types, but here is a self-contained example:
> {-# LANGUAGE MultiParamTypeClasses, FunctionalDependencies,
> FlexibleInstances #-}
>
> data Id=Id String
>
> data Result id =ResultId Id
>| ResultGen id
>
> data Sig id=IdSig Id
>
ge-
> From: haskell-cafe-boun...@haskell.org
> [mailto:haskell-cafe-boun...@haskell.org] On Behalf Of JP Moresmau
> Sent: 16 March 2011 21:46
> To: Haskell Cafe
> Subject: [Haskell-cafe] Could not deduce ... using functional dependencies
> with GHC7
>
> Hello, when moving to GHC
ehalf Of JP Moresmau
Sent: 16 March 2011 21:46
To: Haskell Cafe
Subject: [Haskell-cafe] Could not deduce ... using functional dependencies with
GHC7
Hello, when moving to GHC7 a body of code that I'm not immensely familiar with,
I got an error compiling with GHC 7.0.2. Can somebody kindly exp
Hello, when moving to GHC7 a body of code that I'm not immensely
familiar with, I got an error compiling with GHC 7.0.2. Can somebody
kindly explain to me what it means and how to get around it?
This is in the scion code base so is using some GHC types.
I have a class with a functional dependency
