[英]Using Diagrams library in haskell (draw binary trees)
我正在尝试使用Haskell图库来绘制二叉树。
这是我的树类型:
data Tree a = Empty
| Node { label :: a, left,right :: Tree a }
leaf :: a -> Tree a
leaf a = Node a Empty Empty
这是一棵随机树:
t0 = Node 1 (Node 2 (leaf 3) (leaf 4)) (Node 5 (leaf 6) (leaf 7))
为了在中间画一个带有char的圆,我使用了这个简单的函数(可以正常工作):
diagNode :: String -> Diag
这是我绘制二进制树的代码:
diagTree :: Show s => Tree s -> Diag
diagTree Empty = diagNode "Empty"
diagTree (Node x Empty Empty) = connectOutside "X" "L" $
connectOutside "X" "R" $
nx
===
(nl ||| nr) # center
where
nx = named "X" ( diagNode (show x) )
nl = named "L" (diagNode "Empty" )
nr = named "R" (diagNode "Empty" )
diagTree (Node x left right) = connectOutside "X" "L" $
connectOutside "X" "R" $
nx
===
(nl ||| nr) # center
where
nx = named "X" ( diagNode (show x) )
nl = named "L" (diagTree left )
nr = named "R" (diagTree right )
您可以看到我的代码仅适用于最后的“叶子”,但是它没有将上层节点与下面的节点连接在一起。 我认为问题在于,我递归调用了diagTree。
我该如何解决这个问题?
我认为问题在于您要为内部节点命名,以便connectOutside
连接找到的名字(恰好是树中的最后一个节点)。 您可以通过根据节点的位置为其指定唯一的名称来解决此问题:
diagTree :: Show s => Tree s -> Diagram Rasterific
diagTree = go [] where
go nm Empty = diagNode "Empty" # named nm
go nm (Node x l r) =
connectOutside nm nmL .
connectOutside nm nmR $
nx
===
(nl ||| nr) # centerX
where
(nmL, nmR) = ('L':nm, 'R':nm)
nx = diagNode (show x) # named nm
nl = go nmL l # named nmL
nr = go nmR r # named nmR
与
data Tree a = Empty
| Node { label :: a, left,right :: Tree a }
deriving Show
leaf :: a -> Tree a
leaf a = Node a Empty Empty
diagNode :: String -> Diagram Rasterific
diagNode txt = text txt # fontSizeL 0.4 <> circle 1 & pad 2
我懂了
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