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module Data.Graph.Inductive.Internal.Queue(
-- * Type
Queue(..),
-- * Operations
mkQueue, queuePut, queuePutList, queueGet, queueEmpty
) where
import Data.List (foldl')
data Queue a = MkQueue [a] [a]
mkQueue :: Queue a
mkQueue = MkQueue [] []
queuePut :: a -> Queue a -> Queue a
queuePut item (MkQueue ins outs) = MkQueue (item:ins) outs
queuePutList :: [a] -> Queue a -> Queue a
queuePutList xs q = foldl' (flip queuePut) q xs
queueGet :: Queue a -> (a, Queue a)
queueGet (MkQueue ins (item:rest)) = (item, MkQueue ins rest)
queueGet (MkQueue ins []) = queueGet (MkQueue [] (reverse ins))
queueEmpty :: Queue a -> Bool
queueEmpty (MkQueue ins outs) = null ins && null outs
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