Hm, no instance Arbitrary Char is provided in the QuickCheck modules that came with my hugs or ghc. Probably the author just forgot to import Data.Char. Try inserting that in QuickCheck.hs. Hope that works, Daniel Am Samstag, 9. April 2005 21:10 schrieb Adam Wyner:

Hi,

I'd like to use QuickCheck for testing Haskell programs. I'm using Hugs in Windows. I'm a newbie to Haskell.

Just running QuickCheck.hs itself, which comes with the Hugs98 libraries, I get an error message and the Monad command line, which indicates that quickcheck didn't load.

ERROR "C:\Program Files\Hugs98/libraries\QuickCheck.hs":147 - Undefined variable "chr" Monad>

Here is the line in QuickCheck.hs which leads to the error.

instance Arbitrary Char where arbitrary = choose (32,255) >>= \n -> return (chr n) coarbitrary n = variant (ord n)

This code is from the website:

http://www.cs.chalmers.se/~rjmh/QuickCheck/QuickCheck.hs

I tested it with the following module, as per the instructions in on QuickCheck's manual page: ---- module TestQuickCheck

where

import QuickCheck

prop_RevRev xs = reverse (reverse xs) == xs where types = xs::[Int] ---- Loading just this, I get the same error:

Prelude> :l TestQuickCheck ERROR "C:\Program Files\Hugs98/libraries\QuickCheck.hs":147 - Undefined variable "chr" Monad>

I know others report using QuickCheck, so this problem must have been resolved.

Also, I guess the quickcheck script is for Linux alone? Any scripts for Hugs in Windows?

Cheers, Adam