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module Grasp.IP (
IP,
singleton,
empty,
isEmpty,
peek,
push,
pop,
shift
) where
import Grasp.Types( GNode )
newtype IP = IP [GNode]
deriving (Eq, Show)
singleton :: GNode -> IP
singleton n = IP [n]
empty :: IP
empty = IP []
isEmpty :: IP -> Bool
isEmpty (IP p) = (length p == 0)
peek :: IP -> Maybe GNode
peek (IP p) = if (length p == 0) then Nothing else Just (head p)
push :: GNode -> IP -> IP
push n (IP p) = IP (n:p)
pop :: IP -> IP
pop (IP p) = if (length p == 0) then empty else IP (tail p)
shift :: GNode -> IP -> IP
shift n (IP p) = if (length p == 0) then empty else IP (n:(tail p))
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