1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
|
{-# LANGUAGE TemplateHaskell, RecursiveDo #-}
import Test.QuickCheck
import Control.Monad.Fix
-- A simple (not complete) test for the MonadFix instance.
cyclicList :: Gen [Int]
cyclicList = do
rec xs <- fmap (:ys) arbitrary
ys <- fmap (:xs) arbitrary
return xs
prop_cyclic :: Property
prop_cyclic =
forAll (Blind <$> cyclicList) $ \(Blind xs) ->
-- repeats with period 2
and $ take 100 $ zipWith (==) xs (drop 2 xs)
prop_period2 :: Property
prop_period2 =
expectFailure $
forAll (Blind <$> cyclicList) $ \(Blind xs) ->
-- does not always repeat with period 1
and $ take 100 $ zipWith (==) xs (drop 1 xs)
return []
main = do True <- $quickCheckAll; return ()
|
