FullBinaryTreeOps methods for collecting labels #15
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thomas-stripe
suggested changes
Nov 14, 2016
| def collectLeafLabelsF[A](node: Node, f: LL => A): Set[A] = | ||
| foldNode(node)({case (lc, rc, _) => collectLeafLabelsF(lc, f) | collectLeafLabelsF(rc, f)}, ll => Set(f(ll))) | ||
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| def collectLabels(node: Node): Set[Label] = collectLabelsF(node, identity) |
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This method could go on TreeOps instead, since it's general enough.
| @@ -21,6 +21,17 @@ trait FullBinaryTreeOps[T, BL, LL] extends TreeOps[T, Either[BL, LL]] { | |||
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| def children(node: Node): Iterable[Node] = | |||
| foldNode(node)({ case (lc, rc, _) => lc :: rc :: Nil }, _ => Nil) | |||
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| def collectLabelsF[A](node: Node, f: Label => A): Set[A] = | |||
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If you wanted to, you could implement this w/ reduce:
reduce(node) { case (label, childLabels) => childLabels.foldLeft(Set(label))(_ ++ _) }
Though I'd say there is a case to be made that we should have a FullBinaryTreeOps-specific version of reduce that takes 2 functions, since we shouldn't have to deal with the Iterable childLabels (and it'd make implementing collectLeafLabels in terms of reduce nicer):
def reduceFullBinaryTree[A](node: Node)(f: LL => A)(g: (BL, A, A) => A): A = ???wdyt?
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Included in #19. |
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When writing tests on binary trees, I've occasionally wanted to be able to obtain a list of the trees' keys, to aid in constructing sample data and models.
This PR adds four methods for collecting labels from full binary trees:
collectLabelscollectLabelsFcollectLeafLabelscollectLeafLabelsFThese methods return sets, as we shouldn't have any opinion on the ordering of labels in
FullBinaryTreeOps(ordered traversals should be handled in Brushfire'sTreeTraversals[0]).cc @erik-stripe @kelley-stripe @oscar-stripe @rob-stripe @thomas-stripe
[0] https://github.com/stripe/brushfire/blob/master/brushfire-tree/src/main/scala/com/stripe/brushfire/TreeTraversal.scala