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fix a bug in naive layered and improve docs a little

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This commit is contained in:
Robby Findler 2014-04-21 21:41:45 -05:00
parent c919579e06
commit 3f21371379
2 changed files with 19 additions and 6 deletions
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17
pkgs/pict-pkgs/pict-doc/pict/scribblings/tree-layout.scrbl
View File

@ -68,9 +68,10 @@ that render them as @racket[pict]s.
[#:x-spacing x-spacing (or/c (and/c real? positive?) #f) #f]
[#:y-spacing y-spacing (or/c (and/c real? positive?) #f) #f])
pict?]{
Uses a naive layered algorithm to build the tree.
It recursively constructs subtrees and then horizontally
combines them, aligning them at the tops. Then it places
Uses a naive algorithm that ensures that all nodes at a fixed
depth are the same vertical distance from the root (dubbed ``layered'').
It recursively lays out subtrees and then horizontally
combines them, aligning them at their tops. Then it places
the root node centered over the children nodes.
@examples[#:eval
@ -102,7 +103,9 @@ that render them as @racket[pict]s.
(tree-layout
(tree-layout
(tree-layout
(tree-layout #f #f)
(tree-layout
(tree-layout #f #f)
#f)
#f)
#f)
#f)))
@ -132,6 +135,12 @@ that render them as @racket[pict]s.
as it can, even to the point that one subtree of a given node might cross
under the other one.
More precisely, it recursively lays out the two subtree and then,
without adjusting the layout of the two subtrees, moves them as
close together as it can, putting the root of the new tree centered
on top of its children. (It does this in linear time, using clever
techniques as discussed in the paper.)
The @racket[x-spacing] and @racket[y-spacing] are the amount of space that each
row and each column takes up, measured in pixels. If @racket[x-spacing] is @racket[#f],
it is the width of the widest node @racket[pict?] in the tree.

8
pkgs/pict-pkgs/pict-lib/pict/private/naive-layered.rkt
View File

@ -19,7 +19,9 @@
(define children-pairs
(for/list ([child (in-list children)])
(match child
[#f (cons #f (blank))]
[#f
(define b (blank))
(cons b b)]
[(tree-edge child color)
(loop child)])))
(define this-root (launder (ghost pict)))
@ -106,7 +108,9 @@
(_tree-layout
(_tree-layout
(_tree-layout
(_tree-layout #f #f)
(_tree-layout
(_tree-layout #f #f)
#f)
#f)
#f)
#f)))