On Fri, 12 May 2000, Wilhelm B. Kloke wrote:
> Hi,
>
> I am trying to reproduce the fuzzy oscillator example by Jan Skibinski.
> ( http://www.numeric-quest.com/haskell/Fuzzy_oscillator.html )
> I am having problems to compile the module Fuzzy.hs. As I am
> just in an early learning stage, I need help to understand the error.
>
> hugs98 e.g. says:
>
> Reading file "/usr/local/share/hugs/lib/Prelude.hs":
> Reading file "Fuzzy_oscillator.lhs":
> Reading file "Fuzzy.hs":
> Type checking
> ERROR "Fuzzy.hs" (line 76): Cannot build superclass instance
> *** Instance : Num (a -> b)
> *** Context supplied : Num b
> *** Required superclass : Show (a -> b)
[...]
This subject was already discussed in thread
"Show class on ADT with functions" (original
message by Mike Jones, 2000.05.05). Few answers
were given.
Fuzzy.hs was written long time ago by Warwick
researchers. Similarly, my Fuzzy_oscillator.lhs
is 1.5 years old. I do not have any idea as yet
why Fuzzy used to work with old versions of Hugs.
If someone from Warwick reads these messages
the chance is that they will fix Fuzzy.hs.
If not, I can only promise to look into things and
provide patches for Fuzzy to assure that
Fuzzy_oscillator works again. It needed the face
lift anyway due to the replacement of Gif module
by the newer GD module.
Jan
