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Jun 3, 2017
Merged

add shuffle generator #69

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9 changes: 8 additions & 1 deletion src/Test/QuickCheck/Gen.purs
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Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,7 @@ module Test.QuickCheck.Gen
, listOf
, vectorOf
, elements
, shuffle
, runGen
, evalGen
, perturbGen
Expand All @@ -39,7 +40,7 @@ import Control.Monad.State (State, runState, evalState)
import Control.Monad.State.Class (state, modify)
import Control.Monad.Gen.Class (class MonadGen)

import Data.Array ((!!), length)
import Data.Array ((!!), length, zip, sortBy)
import Data.Enum (class BoundedEnum, fromEnum, toEnum)
import Data.Foldable (fold)
import Data.Int (toNumber, floor)
Expand Down Expand Up @@ -212,6 +213,12 @@ elements (x :| xs) = do
n <- chooseInt zero (length xs)
pure if n == zero then x else fromMaybe x (xs !! (n - one))

-- | Generate a random permutation of the given array
shuffle :: forall a. Array a -> Gen (Array a)
shuffle xs = do
ns <- vectorOf (length xs) (chooseInt 0 top)
pure (map snd (sortBy (comparing fst) (zip ns xs)))

-- | Run a random generator
runGen :: forall a. Gen a -> GenState -> Tuple a GenState
runGen = runState <<< unGen
Expand Down