{-# LANGUAGE FlexibleContexts #-} ----------------------------------------------------------------------------- -- | -- Module : Data.Tree.Lens -- Copyright : (C) 2012-14 Edward Kmett -- License : BSD-style (see the file LICENSE) -- Maintainer : Edward Kmett <ekmett@gmail.com> -- Stability : provisional -- Portability : MTPCs -- ---------------------------------------------------------------------------- module Data.Tree.Lens ( root , branches ) where import Control.Lens import Data.Functor import Data.Tree -- | A 'Lens' that focuses on the root of a 'Tree'. -- -- >>> view root $ Node 42 [] -- 42 root :: Lens' (Tree a) a root f (Node a as) = (`Node` as) <$> f a {-# INLINE root #-} -- | A 'Lens' returning the direct descendants of the root of a 'Tree' -- -- @'view' 'branches' ≡ 'subForest'@ branches :: Lens' (Tree a) [Tree a] branches f (Node a as) = Node a <$> f as {-# INLINE branches #-}