ZipperAG-0.1: src/Language/Grammars/ZipperAG.hs

-- |
-- Module      :  ZipperAG
-- Copyright   :  2013 Pedro Martins
-- License     :  BSD3
--
-- Maintainer  :  Pedro Martins <pedromartins4@gmail.com>
-- Stability   :  Experimental
-- Portability :  Portable
--
-- Zipper-based AG supporting functions
module Language.Grammars.ZipperAG where

import Data.Generics.Zipper
import Data.Maybe

-- |Gives the n'th child
(.$) :: Zipper a -> Int -> Zipper a
z .$ 1 = fromJust (down' z)
z .$ n = fromJust (right ( z.$(n-1) ))

-- |parent
parent = fromJust.up

-- |Tests if z is the n'th sibling
(.|) :: Zipper a -> Int -> Bool
z .| 1 = case (left z) of
			Nothing -> False
			_ -> True
z .| n = case (left z) of
			Nothing -> False
			Just x ->  z .| (n-1)