[Haskell-beginners] upgrade Hackage show to QuickCheck 2 for lambdabot

[Mark Wright]

Hi,

I'm trying to upgrade Hackage show to QuickCheck 2, after
applying the diffs below (which may not be correct, since I am
a beginner), I am left which this error message:

runghc ./Setup.hs build
Preprocessing library show-0.3.4...
Building show-0.3.4...
[4 of 4] Compiling ShowQ            ( ShowQ.hs, dist/build/ShowQ.o )

ShowQ.hs:104:20: Not in scope: `generate'

Compilation exited abnormally with code 1 at Fri Jul  2 23:07:17

The error occurs in this method:

tests :: Gen Result -> StdGen -> Int -> Int -> [[String]] -> IO String
tests gen rnd0 ntest nfail stamps
  | ntest == 500  = done "OK, passed" ntest stamps
  | nfail == 1000 = done "Arguments exhausted after" ntest stamps
  | otherwise = case ok result of
       Nothing    -> tests gen rnd1 ntest (nfail+1) stamps
       Just True  -> tests gen rnd1 (ntest+1) nfail (stamp result:stamps)
       Just False -> return $ "Falsifiable, after "
                               ++ show ntest
                               ++ " tests:\n"
                               ++ reason result
   where
      result      = generate (((+ 3) . (`div` 2)) ntest) rnd2 gen
      (rnd1,rnd2) = split rnd0

The QuickCheck 1 generate method is near the bottom this page:

http://hackage.haskell.org/packages/archive/QuickCheck/1.2.0.0/doc/html/Test-QuickCheck.html

but I can not find generate in QuickCheck 2.  I am wondering if
you have any ideas on how to fix it?

I'm trying to package lambdabot on Solaris.  I have already packaged
the Haskell Platform and about 90 packages, they are in:

http://pkgbuild.sourceforge.net/spec-files-extra/

Thanks very much, Mark

here are the diffs:

goanna% diff -wc show-0.3.4-orig/ShowQ.hs show-0.3.4/ShowQ.hs 
*** show-0.3.4-orig/ShowQ.hs    Wed Jan 20 11:24:11 2010
--- show-0.3.4/ShowQ.hs Fri Jul  2 23:07:13 2010
***************
*** 12,22 ****
--- 12,25 ----
  
  import qualified Test.SmallCheck (smallCheck, Testable)
  import Test.QuickCheck
+ import Test.QuickCheck.Arbitrary
  import Data.Char
  import Data.List
  import Data.Word
  import Data.Int
  import System.Random
+ import Control.Exception (evaluate)
+ import Test.QuickCheck.Property (ok, stamp)
  
  type T = [Int]
  type I = Int
***************
*** 23,36 ****
--- 26,45 ----
  
  instance Arbitrary Char where
      arbitrary     = choose (minBound, maxBound)
+     
+ instance CoArbitrary Char where
      coarbitrary c = variant (ord c `rem` 4)
  
  instance Arbitrary Word8 where
      arbitrary = choose (minBound, maxBound)
+     
+ instance CoArbitrary Word8 where
      coarbitrary c = variant (fromIntegral ((fromIntegral c) `rem` 4))
  
  instance Arbitrary Ordering where
      arbitrary     = elements [LT,EQ,GT]
+ 
+ instance CoArbitrary Ordering where
      coarbitrary LT = variant 1
      coarbitrary EQ = variant 2
      coarbitrary GT = variant 0
***************
*** 37,42 ****
--- 46,53 ----
  
  instance Arbitrary Int64 where
    arbitrary     = sized $ \n -> choose (-fromIntegral n,fromIntegral n)
+   
+ instance CoArbitrary Int64 where
    coarbitrary n = variant (fromIntegral (if n >= 0 then 2*n else 2*(-n) + 1))
  
  instance (Integral a, Arbitrary a) => Arbitrary (Ratio a) where
***************
*** 48,53 ****
--- 59,65 ----
                              else (b % a)
                           else (a % b)
  
+ instance (Integral a, CoArbitrary a) => CoArbitrary (Ratio a) where
    coarbitrary m = variant (fromIntegral $ if n >= 0 then 2*n else 2*(-n) + 1)
      where n = numerator m
  
***************
*** 87,93 ****
         Just False -> return $ "Falsifiable, after "
                                 ++ show ntest
                                 ++ " tests:\n"
!                                ++ unlines (arguments result)
     where
        result      = generate (((+ 3) . (`div` 2)) ntest) rnd2 gen
        (rnd1,rnd2) = split rnd0
--- 99,105 ----
         Just False -> return $ "Falsifiable, after "
                                 ++ show ntest
                                 ++ " tests:\n"
!                                ++ reason result
     where
        result      = generate (((+ 3) . (`div` 2)) ntest) rnd2 gen
        (rnd1,rnd2) = split rnd0
goanna%