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ALGO: generalize the QuadTree folds 

Now we traverse over all nodes (TNode, TLeaf, TNil),
not just TLeaf.
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hasufell 2014-11-18 00:56:24 +01:00
parent 8d7ed598e2
commit 7527e0bec3
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1 changed files with 8 additions and 7 deletions
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15
Algorithms/QuadTree/QuadTree.hs
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@ -121,15 +121,16 @@ getSquareByZipper sq z = go sq (reverse . snd $ z)
go sq' (SECrumb {}:zs) = go (seSq sq') zs
-- |Left fold over the tree leafs.
qtFoldl :: (a -> b -> a) -> a -> QuadTree b -> a
qtFoldl _ sv (TNil) = sv
qtFoldl f sv (TLeaf a) = f sv a
qtFoldl f sv (TNode nw ne sw se) = foldl (qtFoldl f) sv [nw, ne, sw, se]
-- |Left fold over the tree.
qtFoldl :: (a -> QuadTree b -> a) -> a -> QuadTree b -> a
qtFoldl f sv qt@(TNode nw ne sw se) = foldl (qtFoldl f)
(f sv qt)
[nw, ne, sw, se]
qtFoldl f sv qt = f sv qt
-- |Right fold over the tree leafs.
qtFoldr :: (b -> a -> a) -> a -> QuadTree b -> a
-- |Right fold over the tree.
qtFoldr :: (QuadTree b -> a -> a) -> a -> QuadTree b -> a
qtFoldr f sv qt = qtFoldl (\g b x -> g (f b x)) id qt sv