HI,
For darwinports users on Mac OS X who just have to live on the
bleeding edge, a new port of the development version of GHC
is available.
It builds from the latest cvs. (So you take your chances. There's no
guarantee that the build process will work, not trash your machine,
not render your city
In the case where a datasource is determined by 's' and 'k', we need to
return a different
type depending on sucess or failure:
>data TJust t = TJust t
>data TNothing = TNothing
>
>class Datasource s k v | s k -> v where
>dsread :: s -> k -> v
>instance (Datasource l k v',Datasource r k v'',D
Not at all... You can have Datasource s k v | s k -> v ... but I have't
time to do it now...
By the way that wasn't the change I was talking about!
class Datasource' z l r k v | z l r k -> v
The 'z' was missing from your fundep.
Keean.
Robert van Herk wrote:
See change above!
Also note type o
Some more fixes...
Keean Schupke wrote:
Hi Keean,
First of all, thank you for your answers. I have tried your solution
using TypeEq.
instance (Datasource l k' v', TypeEq k k' z, Datasource' z l r k v) =>
Datasource (JoinedDS l r) k v where
_dsread (JoinedDS refl refr) k = do { l <- readIORef re
See change above!
Also note type of fundep for Datasource should now be:
class Datasource s k v | s -> k v where ...
I see But the cool thing was, that my datasources were generic, in
the sence that they could store multiple k's and v's. Now, they would be
unique for the actual storage mech
Sorry, oops again:
The problem is that it complains that it cannot find an instance for
Datasource' z [MyKeyVal] [MyKeyVal] Float Int
Whilst I have an instance
Datasource [MyKeyVal] Float Int
Thus, it seems that it needs an explicit type for the z here.
Both datasources stored in the joined datas
Robert van Herk wrote:
Sorry, this is the compiler error I get:
No instances for (KeyHasValue MyKeyVal k' v',
Datasource.Tools.FakePrelude.TypeEq Float k' z,
Datasource' z [MyKeyVal] [MyKeyVal] Float Int)
When I am trying to do
do { createJoinedDS' x x;
Sorry, this is the compiler error I get:
No instances for (KeyHasValue MyKeyVal k' v',
Datasource.Tools.FakePrelude.TypeEq Float k' z,
Datasource' z [MyKeyVal] [MyKeyVal] Float Int)
When I am trying to do
do { createJoinedDS' x x;
(joined,(v::Mayb
Hi Keean,
First of all, thank you for your answers. I have tried your solution
using TypeEq.
instance (Datasource l k' v', TypeEq k k' z, Datasource' z l r k v) =>
Datasource (JoinedDS l r) k v where
_dsread (JoinedDS refl refr) k = do { l <- readIORef refl;
