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Today's Topics:
1. upgrade Hackage show to QuickCheck 2 for lambdabot (Mark Wright)
2. Re: Re: Enforcing Monad Laws (Brandon S Allbery KF8NH)
----------------------------------------------------------------------
Message: 1
Date: Fri, 2 Jul 2010 23:49:36 +1000
From: Mark Wright <[email protected]>
Subject: [Haskell-beginners] upgrade Hackage show to QuickCheck 2 for
lambdabot
To: [email protected]
Message-ID: <[email protected]>
Content-Type: text/plain; charset=us-ascii
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%
------------------------------
Message: 2
Date: Fri, 02 Jul 2010 11:12:54 -0400
From: Brandon S Allbery KF8NH <[email protected]>
Subject: Re: [Haskell-beginners] Re: Enforcing Monad Laws
To: [email protected]
Message-ID: <[email protected]>
Content-Type: text/plain; charset=UTF-8
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
On 7/2/10 04:04 , Heinrich Apfelmus wrote:
> Jorden M wrote:
>> C++ `Concepts', which almost made it into the C++0x standard, are
>> roughly similar to Haskell type classes. The proposal for concepts in
>> C++ had a feature called axioms, which allow the programmer to specify
>> semantics on the functions the concept contains. This allows for
>> enforcing things such as the Monad Laws, as well as letting the
>> compiler make certain optimizations it may not have been able to make
>> without axiomatic guarantees.
>
> I have a hard time imagining that axioms are being used to prove properties
> about programs in a language such as C++... :) Any pointers?
I just took a look at it, and Concepts look to me like Haskell
contexts/constraints; an example is:
> concept LessThanComparable<typename T> {
> bool operator<(const T& x, const T& y);
> }
>
> template<typename T>
> requires LessThanComparable<T>
> const T& min(const T& x, const T& y) {
> return x < y? x : y;
> }
which is obviously just an Ord costraint on min().
(My initial thought before looking at this was that it was programming by
contract, or possibly just making invariants explicit; the latter wouldn't
actually prove anything, though.)
- --
brandon s. allbery [linux,solaris,freebsd,perl] [email protected]
system administrator [openafs,heimdal,too many hats] [email protected]
electrical and computer engineering, carnegie mellon university KF8NH
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