[Haskell-cafe] [Newbie] Cannot derive Eq and Show. Why?

Bulat Ziganshin bulat.ziganshin at gmail.com
Sat Sep 9 04:09:37 EDT 2006

Hello Peter,

Friday, September 8, 2006, 6:03:36 PM, you wrote:

> I am stumped again. The following code generates the error "ERROR
> file:.\Cube.hs:12 - An instance of IArray UArray a is required to derive Eq
> (Cube a b)" in Hugs. But I did specify the IArray UArray k constraint. So
> what is wrong?

> data (Ord k, IArray UArray k, IArray UArray v) =>

shortly speaking, you should either use boxed Array or switch to using
my ArrayRef library which supports polymorphic unboxed arrays

look for detailed explanations of problem to

ArrayRef library can be found at http://haskell.org/haskellwiki/Library/ArrayRef

for use with Hugs it need to be preprocessed via one of included
MakeHugs scripts

i have added your module to the library as the shortest example of using
polymorphic unboxed arrays :)  see attached file. of course, if you
want that this file will be removed or modified, i will do

Best regards,
 Bulat                            mailto:Bulat.Ziganshin at gmail.com
-------------- next part --------------
A non-text attachment was scrubbed...
Name: cube.hs
Type: application/octet-stream
Size: 422 bytes
Desc: not available
Url : http://www.haskell.org//pipermail/haskell-cafe/attachments/20060909/1c40bc1a/cube.obj

More information about the Haskell-Cafe mailing list