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1+module Regression.T11 (test11) where
2+
3+import Data.Bool
4+import Control.Monad.Ether
5+
6+import qualified Control.Monad.State as T
7+import qualified Control.Monad.Reader as T
8+
9+import Test.Tasty
10+import Test.Tasty.QuickCheck
11+
12+data STag
13+
14+testEther
15+ :: ( MonadState STag [Integer] m
16+ , T.MonadState Bool m
17+ , T.MonadReader Integer m )
18+ => m ()
19+testEther = do
20+ T.modify not
21+ f <- bool negate id <$> T.get
22+ n <- T.ask
23+ T.local succ testEther
24+ modify @STag (f n:)
25+
26+model :: Integer -> [Integer]
27+model n = zipWith ($) (cycle [id, negate]) [n..]
28+
29+runner1 n
30+ = flip (T.runReader) n
31+ . flip (execStateT @STag) []
32+ . flip T.evalStateT False
33+
34+runner2 n
35+ = flip T.evalState False
36+ . flip (execStateT @STag) []
37+ . flip T.runReaderT n
38+
39+test11 :: TestTree
40+test11 = testGroup "T11: Lazy sequence"
41+ [ testProperty "runner₁ works"
42+ $ \l n -> property
43+ $ take l (runner1 n testEther) == take l (model n)
44+ , testProperty "runner₂ works"
45+ $ \l n -> property
46+ $ take l (runner2 n testEther) == take l (model n)
47+ , testProperty "runner₁ == runner₂"
48+ $ \l n -> property
49+ $ take l (runner1 n testEther) == take l (runner2 n testEther)
50+ ]