module DataStructures.SlowQueue_Work where



------------------------------------------------------------
-- Interface

empty   :: Q a
add     :: a -> Q a -> Q a
remove  :: Q a -> Q a
front   :: Q a -> a
isEmpty :: Q a -> Bool

-- Abstract data type



------------------------------------------------------------
-- Implementation

data Q a = Q [a]
  deriving (Eq, Show)

empty             = Q []
add a (Q as)      = Q (as ++ [a])
remove (Q (a:as)) = Q as
front (Q (a:as))  = a
isEmpty (Q as)    = null as