Rank.hs

{-# LANGUAGE TypeApplications #-}
module QuickCheck.Rank where
import Data.Bool

import Data.Eq (Eq(..))
import Data.Function (($))
import Data.Functor ((<$>))
import Data.Ratio (numerator)
import Prelude (Enum(..), (*), fromIntegral)
import Test.Tasty
import Test.Tasty.QuickCheck
import qualified Data.List as List

import Majority.Merit
import Majority.Value
import Majority.Rank
import Types
import QuickCheck.Value ()

quickcheck :: TestTree
quickcheck =
	testGroup "Rank"
	 [ testGroup "majorityValueOfRank . rankOfMajorityValue == id"
		 [ testProperty "SchoolGrade" $ testMVRankMV @SchoolGrade
		 , testProperty "DanishSchoolGrade" $ testMVRankMV @DanishSchoolGrade
		 ]
	 ]

testMVRankMV :: forall g. Enum g => MajorityValue g -> Bool
testMVRankMV mv =
	let gs = fromIntegral $ List.length (enumFrom (toEnum 0) :: [g]) in
	let js = numerator $ (2 *) $ List.sum $ middleShare <$> unMajorityValue mv in
	majorityValueOfRank js gs (rankOfMajorityValue gs mv') == mv'
	where
	ranked a = Ranked (fromIntegral (fromEnum a), ())
	mv' = MajorityValue $
		(<$> unMajorityValue mv) $ \(Middle s l h) ->
			Middle s (ranked l) (ranked h)