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+ GNU GENERAL PUBLIC LICENSE
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+ END OF TERMS AND CONDITIONS
+
+ How to Apply These Terms to Your New Programs
+
+ If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these terms.
+
+ To do so, attach the following notices to the program. It is safest
+to attach them to the start of each source file to most effectively
+state the exclusion of warranty; and each file should have at least
+the "copyright" line and a pointer to where the full notice is found.
+
+ <one line to give the program's name and a brief idea of what it does.>
+ Copyright (C) <year> <name of author>
+
+ This program is free software: you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation, either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+Also add information on how to contact you by electronic and paper mail.
+
+ If the program does terminal interaction, make it output a short
+notice like this when it starts in an interactive mode:
+
+ <program> Copyright (C) <year> <name of author>
+ This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
+ This is free software, and you are welcome to redistribute it
+ under certain conditions; type `show c' for details.
+
+The hypothetical commands `show w' and `show c' should show the appropriate
+parts of the General Public License. Of course, your program's commands
+might be different; for a GUI interface, you would use an "about box".
+
+ You should also get your employer (if you work as a programmer) or school,
+if any, to sign a "copyright disclaimer" for the program, if necessary.
+For more information on this, and how to apply and follow the GNU GPL, see
+<http://www.gnu.org/licenses/>.
+
+ The GNU General Public License does not permit incorporating your program
+into proprietary programs. If your program is a subroutine library, you
+may consider it more useful to permit linking proprietary applications with
+the library. If this is what you want to do, use the GNU Lesser General
+Public License instead of this License. But first, please read
+<http://www.gnu.org/philosophy/why-not-lgpl.html>.
--- /dev/null
+module Data.TreeSeq.Strict.Zipper where
+
+import Control.Arrow (Kleisli(..))
+import Control.Category (Category(..), (>>>))
+import Control.Applicative (Applicative(..), Alternative(..))
+import Data.Bool
+import Data.Eq (Eq)
+import Data.Function (($))
+import Data.Functor ((<$>))
+import Data.Int (Int)
+import Data.List.NonEmpty (NonEmpty(..))
+import Data.Maybe (Maybe(..), maybe, mapMaybe)
+import Data.Monoid (Monoid(..))
+import Data.Semigroup (Semigroup(..))
+import Data.Sequence (ViewL(..), ViewR(..), (<|), (|>))
+import Data.Typeable (Typeable)
+import Prelude (undefined)
+import Text.Show (Show(..))
+import qualified Data.List as List
+import qualified Data.List.NonEmpty as NonEmpty
+import qualified Data.Sequence as Seq
+
+import Data.TreeSeq.Strict (Trees, Tree(..))
+
+-- * Type 'Zipper'
+type Zipper a = NonEmpty (Cursor a)
+
+-- | Return a 'Zipper' starting at the given 'Tree'.
+zipper :: Tree a -> Zipper a
+zipper t = Cursor mempty t mempty :| []
+
+-- | Return a 'Zipper' starting at the left-most 'Tree' of the given 'Trees'.
+zippers :: Trees a -> [Zipper a]
+zippers ts =
+ case Seq.viewl ts of
+ EmptyL -> empty
+ l :< ls -> pure $ Cursor mempty l ls :| []
+
+-- | Return the 'Cursor' after zipping the given 'Zipper' upto its last parent.
+root :: Zipper a -> Cursor a
+root = NonEmpty.head . List.last . runAxis axis_ancestor_or_self
+
+-- | Like 'root', but concatenate the 'Cursor' into a 'Trees'.
+roots :: Zipper a -> Trees a
+roots z = ps <> (s <| fs)
+ where Cursor ps s fs = root z
+
+-- | Return the keys within the 'Tree' nodes
+-- leading to the current 'Cursor' of the given 'Zipper'.
+zipath :: Zipper a -> [a]
+zipath z =
+ List.reverse $
+ unTree . cursor_self
+ <$> NonEmpty.toList z
+
+-- | Return the 'Tree's selected by the given 'Axis' from the given 'Zipper'.
+select :: Axis a -> Zipper a -> [Tree a]
+select axis z = cursor_self . NonEmpty.head <$> runAxis axis z
+
+-- | Return the filtered values selected by the given 'Axis' from the given 'Zipper'.
+filter :: Axis a -> (Zipper a -> Maybe b) -> Zipper a -> [b]
+filter axis f z = f `mapMaybe` runAxis axis z
+
+-- ** Type 'Cursor'
+data Cursor a
+ = Cursor
+ { cursor_preceding_siblings :: Trees a
+ , cursor_self :: Tree a
+ , cursor_following_siblings :: Trees a
+ } deriving (Eq, Show, Typeable)
+
+-- | Return the current 'Cursor' of a 'Zipper'.
+cursor :: Zipper a -> Cursor a
+cursor = NonEmpty.head
+
+-- | Set the current 'Cursor' of a 'Zipper'.
+setCursor :: Zipper a -> Cursor a -> Zipper a
+setCursor (_c :| cs) c = c :| cs
+
+-- | Return the 'Tree' currently under the 'Cursor'.
+current :: Zipper a -> Tree a
+current (Cursor _ t _ :| _) = t
+
+-- ** Type 'Axis'
+type Axis a = AxisAlt [] a
+
+runAxis :: Axis a -> Zipper a -> [Zipper a]
+runAxis = runKleisli
+
+-- ** Type 'AxisAlt'
+-- | Like 'Axis', but generalized with 'Alternative'.
+--
+-- Useful to return a 'Maybe' instead of a list.
+type AxisAlt f a = Kleisli f (Zipper a) (Zipper a)
+
+runAxisAlt :: AxisAlt f a -> Zipper a -> f (Zipper a)
+runAxisAlt = runKleisli
+
+-- ** Axis @repeat@
+-- | Collect all 'Zipper's along a given axis,
+-- including the first 'Zipper'.
+axis_repeat :: AxisAlt Maybe a -> Axis a
+axis_repeat f = Kleisli $ \z -> z : maybe [] (runAxis $ axis_repeat f) (runAxisAlt f z)
+
+-- | Collect all 'Zipper's along a given axis,
+-- excluding the starting 'Zipper'.
+axis_repeat_without_self :: AxisAlt Maybe a -> Axis a
+axis_repeat_without_self f = Kleisli $ \z -> maybe [] (runAxis $ axis_repeat f) (runAxisAlt f z)
+
+-- ** Axis @filter@
+axis_filter :: Axis a -> (Zipper a -> Bool) -> Axis a
+axis_filter axis f = Kleisli $ \z -> List.filter f (runAxis axis z)
+infixl 5 `axis_filter`
+
+axis_filter_current :: Axis a -> (Tree a -> Bool) -> Axis a
+axis_filter_current axis f = Kleisli $ \z -> List.filter (f . current) (runAxis axis z)
+infixl 5 `axis_filter_current`
+
+-- ** Axis @first@
+axis_first :: Axis a -> Axis a
+axis_first axis = Kleisli $ List.take 1 . runAxis axis
+
+-- ** Axis @last@
+axis_last :: Axis a -> Axis a
+axis_last axis = Kleisli $ List.take 1 . List.reverse . runAxis axis
+
+-- ** Axis @at@
+axis_at :: Alternative f => Axis a -> Int -> AxisAlt f a
+axis_at axis i = Kleisli $ \z ->
+ case List.drop i $ runAxis axis z of
+ [] -> empty
+ a:_ -> pure a
+infixl 5 `axis_at`
+
+-- ** Axis @self@
+axis_self :: Applicative f => AxisAlt f a
+axis_self = Kleisli pure
+
+-- ** Axis @child@
+axis_child :: Axis a
+axis_child =
+ axis_child_first >>>
+ axis_repeat axis_following_sibling_nearest
+
+axis_child_lookup_first :: Alternative f => (a -> Bool) -> AxisAlt f a
+axis_child_lookup_first fa = Kleisli $ listHead . runAxis (axis_child_lookup fa)
+
+axis_child_lookup :: (a -> Bool) -> Axis a
+axis_child_lookup f = Kleisli $ \z@(Cursor _ps t _fs :| _) ->
+ let ns = subTrees t in
+ (<$> Seq.findIndicesL (f . unTree) ns) $ \i ->
+ let (ps, ps') = Seq.splitAt i ns in
+ case Seq.viewl ps' of
+ EmptyL -> undefined
+ l :< ls -> Cursor ps l ls :| NonEmpty.toList z
+
+axis_child_first :: Alternative f => AxisAlt f a
+axis_child_first = Kleisli $ \z@(Cursor _ps t _fs :| _) ->
+ case Seq.viewl $ subTrees t of
+ EmptyL -> empty
+ l :< ls -> pure $ Cursor mempty l ls :| NonEmpty.toList z
+
+axis_child_last :: Alternative f => AxisAlt f a
+axis_child_last = Kleisli $ \z@(Cursor _ps t _fs :| _) ->
+ case Seq.viewr $ subTrees t of
+ EmptyR -> empty
+ rs :> r -> pure $ Cursor rs r mempty :| NonEmpty.toList z
+
+-- ** Axis @ancestor@
+axis_ancestor :: Axis a
+axis_ancestor = axis_repeat_without_self axis_parent
+
+axis_ancestor_or_self :: Axis a
+axis_ancestor_or_self = axis_repeat axis_parent
+
+axis_root :: Alternative f => AxisAlt f a
+axis_root = Kleisli $ pure . List.last . runAxis axis_ancestor_or_self
+
+-- ** Axis @descendant@
+axis_descendant_or_self :: Axis a
+axis_descendant_or_self =
+ Kleisli $ collect_child []
+ where
+ collect_child acc z =
+ z : maybe acc
+ (collect_following_first acc)
+ (runAxisAlt axis_child_first z)
+ collect_following_first acc z =
+ collect_child
+ (maybe acc
+ (collect_following_first acc)
+ (runAxisAlt axis_following_sibling_nearest z)
+ ) z
+
+axis_descendant_or_self_reverse :: Axis a
+axis_descendant_or_self_reverse = Kleisli go
+ where go z = z : List.concatMap go (List.reverse $ runAxis axis_child z)
+
+axis_descendant :: Axis a
+axis_descendant = Kleisli $ List.tail . runAxis axis_descendant_or_self
+
+-- ** Axis @preceding@
+axis_preceding_sibling :: Axis a
+axis_preceding_sibling = axis_repeat_without_self axis_preceding_sibling_nearest
+
+axis_preceding_sibling_nearest :: Alternative f => AxisAlt f a
+axis_preceding_sibling_nearest = Kleisli $ \(Cursor ps t fs :| cs) ->
+ case Seq.viewr ps of
+ EmptyR -> empty
+ rs :> r -> pure $ Cursor rs r (t <| fs) :| cs
+
+axis_preceding_sibling_farthest :: Alternative f => AxisAlt f a
+axis_preceding_sibling_farthest = Kleisli $ \z@(Cursor ps t fs :| cs) ->
+ case Seq.viewl (ps |> t) of
+ EmptyL -> pure z
+ l :< ls -> pure $ Cursor mempty l (ls<>fs) :| cs
+
+axis_preceding :: Axis a
+axis_preceding =
+ axis_ancestor_or_self >>>
+ axis_preceding_sibling >>>
+ axis_descendant_or_self_reverse
+
+-- ** Axis @following@
+axis_following_sibling :: Axis a
+axis_following_sibling = axis_repeat_without_self axis_following_sibling_nearest
+
+axis_following_sibling_nearest :: Alternative f => AxisAlt f a
+axis_following_sibling_nearest = Kleisli $ \(Cursor ps t fs :| cs) ->
+ case Seq.viewl fs of
+ EmptyL -> empty
+ l :< ls -> pure $ Cursor (ps |> t) l ls :| cs
+
+axis_following_sibling_farthest :: Alternative f => AxisAlt f a
+axis_following_sibling_farthest = Kleisli $ \z@(Cursor ps t fs :| cs) ->
+ case Seq.viewr (t <| fs) of
+ EmptyR -> pure z
+ rs :> r -> pure $ Cursor (ps<>rs) r mempty :| cs
+
+axis_following :: Axis a
+axis_following =
+ axis_ancestor_or_self >>>
+ axis_following_sibling >>>
+ axis_descendant_or_self
+
+-- ** Axis @parent@
+axis_parent :: Alternative f => AxisAlt f a
+axis_parent = Kleisli $ \(Cursor ps t fs :| cs) ->
+ case cs of
+ Cursor ps' (Tree a _) fs' : cs' ->
+ pure $ Cursor ps' (Tree a $ (ps |> t) <> fs) fs' :| cs'
+ _ -> empty
+
+-- * Utilities
+listHead :: Alternative f => [a] -> f a
+listHead [] = empty
+listHead (a:_) = pure a
sourcephile / git / haskell / treeseq.git / commitdiff