[Haskell-cafe] need help on exercise

Graham Klyne GK at ninebynine.org
Sat Jun 26 05:01:19 EDT 2004

At 17:39 25/06/04 -0400, kasager wrote:
>   I am working on exercise 12.5 from "Haskell, The Craft of Functional
>Programming, second edition" by Simon Thompson.  It asks to make Int an
>instance in the Visible class.  I have tried multiple ways of doing this
>however I keep receiving the same error messege when I compile my program,
>saying that my types do not match and i have given a (Num a, Visible a) =>
>String, when it is supposed to be an Int -> String.  If anyone could help me
>with this issue it would be greatly appreciated.  Thanks, Kelly

 From your description, it looks as if you could have syntax problems with 
the class instance declaration.  It would help if you posted the offending 
code excerpt and message.

As far as I can tell, the exercise does not call for use of context 
declarations (... => ...).


Graham Klyne
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