never executed always true always false

    1 -- | A tiny wrapper around 'IntSet.IntSet' for representing sets of 'Enum'
    2 -- things.
    3 module GHC.Data.EnumSet
    4     ( EnumSet
    5     , member
    6     , insert
    7     , delete
    8     , toList
    9     , fromList
   10     , empty
   11     , difference
   12     ) where
   13 
   14 import GHC.Prelude
   15 
   16 import qualified Data.IntSet as IntSet
   17 
   18 newtype EnumSet a = EnumSet IntSet.IntSet
   19 
   20 member :: Enum a => a -> EnumSet a -> Bool
   21 member x (EnumSet s) = IntSet.member (fromEnum x) s
   22 
   23 insert :: Enum a => a -> EnumSet a -> EnumSet a
   24 insert x (EnumSet s) = EnumSet $ IntSet.insert (fromEnum x) s
   25 
   26 delete :: Enum a => a -> EnumSet a -> EnumSet a
   27 delete x (EnumSet s) = EnumSet $ IntSet.delete (fromEnum x) s
   28 
   29 toList :: Enum a => EnumSet a -> [a]
   30 toList (EnumSet s) = map toEnum $ IntSet.toList s
   31 
   32 fromList :: Enum a => [a] -> EnumSet a
   33 fromList = EnumSet . IntSet.fromList . map fromEnum
   34 
   35 empty :: EnumSet a
   36 empty = EnumSet IntSet.empty
   37 
   38 difference :: EnumSet a -> EnumSet a -> EnumSet a
   39 difference (EnumSet a) (EnumSet b) = EnumSet (IntSet.difference a b)