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author | Martin Odersky <odersky@gmail.com> | 2015-09-12 11:38:00 +0200 |
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committer | Martin Odersky <odersky@gmail.com> | 2015-09-12 12:36:57 +0200 |
commit | 5386c88b6e8d2f2ccf68e7d4e14b5fde6faf562f (patch) | |
tree | dd65496a2fae68a8efefd9e877c4c356ec2650a5 /tests/pos | |
parent | 6fc42dd9ea03e30f475e4eaec3e1bf95c35de0d0 (diff) | |
download | dotty-5386c88b6e8d2f2ccf68e7d4e14b5fde6faf562f.tar.gz dotty-5386c88b6e8d2f2ccf68e7d4e14b5fde6faf562f.tar.bz2 dotty-5386c88b6e8d2f2ccf68e7d4e14b5fde6faf562f.zip |
Fix desugaring problem
Desugaring worked incorrectly when both context bounds and default parameters were present.
Diffstat (limited to 'tests/pos')
-rw-r--r-- | tests/pos/rbtree.scala | 565 |
1 files changed, 565 insertions, 0 deletions
diff --git a/tests/pos/rbtree.scala b/tests/pos/rbtree.scala new file mode 100644 index 000000000..1401a1231 --- /dev/null +++ b/tests/pos/rbtree.scala @@ -0,0 +1,565 @@ +/* __ *\ +** ________ ___ / / ___ Scala API ** +** / __/ __// _ | / / / _ | (c) 2005-2013, LAMP/EPFL ** +** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ ** +** /____/\___/_/ |_/____/_/ | | ** +** |/ ** +\* */ + + + +package scala +package collection +package immutable + +import scala.annotation.tailrec +import scala.annotation.meta.getter + +/** An object containing the RedBlack tree implementation used by for `TreeMaps` and `TreeSets`. + * + * Implementation note: since efficiency is important for data structures this implementation + * uses `null` to represent empty trees. This also means pattern matching cannot + * easily be used. The API represented by the RedBlackTree object tries to hide these + * optimizations behind a reasonably clean API. + * + * @since 2.10 + */ +private[collection] +object RedBlackTree { + + def isEmpty(tree: Tree[_, _]): Boolean = tree eq null + + def contains[A: Ordering](tree: Tree[A, _], x: A): Boolean = lookup(tree, x) ne null + def get[A: Ordering, B](tree: Tree[A, B], x: A): Option[B] = lookup(tree, x) match { + case null => None + case tree => Some(tree.value) + } + + @tailrec + def lookup[A, B](tree: Tree[A, B], x: A)(implicit ordering: Ordering[A]): Tree[A, B] = if (tree eq null) null else { + val cmp = ordering.compare(x, tree.key) + if (cmp < 0) lookup(tree.left, x) + else if (cmp > 0) lookup(tree.right, x) + else tree + } + + def count(tree: Tree[_, _]) = if (tree eq null) 0 else tree.count + /** + * Count all the nodes with keys greater than or equal to the lower bound and less than the upper bound. + * The two bounds are optional. + */ + def countInRange[A](tree: Tree[A, _], from: Option[A], to:Option[A])(implicit ordering: Ordering[A]) : Int = + if (tree eq null) 0 else + (from, to) match { + // with no bounds use this node's count + case (None, None) => tree.count + // if node is less than the lower bound, try the tree on the right, it might be in range + case (Some(lb), _) if ordering.lt(tree.key, lb) => countInRange(tree.right, from, to) + // if node is greater than or equal to the upper bound, try the tree on the left, it might be in range + case (_, Some(ub)) if ordering.gteq(tree.key, ub) => countInRange(tree.left, from, to) + // node is in range so the tree on the left will all be less than the upper bound and the tree on the + // right will all be greater than or equal to the lower bound. So 1 for this node plus + // count the subtrees by stripping off the bounds that we don't need any more + case _ => 1 + countInRange(tree.left, from, None) + countInRange(tree.right, None, to) + + } + def update[A: Ordering, B, B1 >: B](tree: Tree[A, B], k: A, v: B1, overwrite: Boolean): Tree[A, B1] = blacken(upd(tree, k, v, overwrite)) + def delete[A: Ordering, B](tree: Tree[A, B], k: A): Tree[A, B] = blacken(del(tree, k)) + def rangeImpl[A: Ordering, B](tree: Tree[A, B], from: Option[A], until: Option[A]): Tree[A, B] = (from, until) match { + case (Some(from), Some(until)) => this.range(tree, from, until) + case (Some(from), None) => this.from(tree, from) + case (None, Some(until)) => this.until(tree, until) + case (None, None) => tree + } + def range[A: Ordering, B](tree: Tree[A, B], from: A, until: A): Tree[A, B] = blacken(doRange(tree, from, until)) + def from[A: Ordering, B](tree: Tree[A, B], from: A): Tree[A, B] = blacken(doFrom(tree, from)) + def to[A: Ordering, B](tree: Tree[A, B], to: A): Tree[A, B] = blacken(doTo(tree, to)) + def until[A: Ordering, B](tree: Tree[A, B], key: A): Tree[A, B] = blacken(doUntil(tree, key)) + + def drop[A: Ordering, B](tree: Tree[A, B], n: Int): Tree[A, B] = blacken(doDrop(tree, n)) + def take[A: Ordering, B](tree: Tree[A, B], n: Int): Tree[A, B] = blacken(doTake(tree, n)) + def slice[A: Ordering, B](tree: Tree[A, B], from: Int, until: Int): Tree[A, B] = blacken(doSlice(tree, from, until)) + + def smallest[A, B](tree: Tree[A, B]): Tree[A, B] = { + if (tree eq null) throw new NoSuchElementException("empty map") + var result = tree + while (result.left ne null) result = result.left + result + } + def greatest[A, B](tree: Tree[A, B]): Tree[A, B] = { + if (tree eq null) throw new NoSuchElementException("empty map") + var result = tree + while (result.right ne null) result = result.right + result + } + + + def foreach[A,B,U](tree:Tree[A,B], f:((A,B)) => U):Unit = if (tree ne null) _foreach(tree,f) + + private[this] def _foreach[A, B, U](tree: Tree[A, B], f: ((A, B)) => U): Unit = { + if (tree.left ne null) _foreach(tree.left, f) + f((tree.key, tree.value)) + if (tree.right ne null) _foreach(tree.right, f) + } + + def foreachKey[A, U](tree:Tree[A,_], f: A => U):Unit = if (tree ne null) _foreachKey(tree,f) + + private[this] def _foreachKey[A, U](tree: Tree[A, _], f: A => U): Unit = { + if (tree.left ne null) _foreachKey(tree.left, f) + f((tree.key)) + if (tree.right ne null) _foreachKey(tree.right, f) + } + + def iterator[A: Ordering, B](tree: Tree[A, B], start: Option[A] = None): Iterator[(A, B)] = new EntriesIterator(tree, start) + def keysIterator[A: Ordering](tree: Tree[A, _], start: Option[A] = None): Iterator[A] = new KeysIterator(tree, start) + def valuesIterator[A: Ordering, B](tree: Tree[A, B], start: Option[A] = None): Iterator[B] = new ValuesIterator(tree, start) + + @tailrec + def nth[A, B](tree: Tree[A, B], n: Int): Tree[A, B] = { + val count = this.count(tree.left) + if (n < count) nth(tree.left, n) + else if (n > count) nth(tree.right, n - count - 1) + else tree + } + + def isBlack(tree: Tree[_, _]) = (tree eq null) || isBlackTree(tree) + + private[this] def isRedTree(tree: Tree[_, _]) = tree.isInstanceOf[RedTree[_, _]] + private[this] def isBlackTree(tree: Tree[_, _]) = tree.isInstanceOf[BlackTree[_, _]] + + private[this] def blacken[A, B](t: Tree[A, B]): Tree[A, B] = if (t eq null) null else t.black + + private[this] def mkTree[A, B](isBlack: Boolean, k: A, v: B, l: Tree[A, B], r: Tree[A, B]) = + if (isBlack) BlackTree(k, v, l, r) else RedTree(k, v, l, r) + + private[this] def balanceLeft[A, B, B1 >: B](isBlack: Boolean, z: A, zv: B, l: Tree[A, B1], d: Tree[A, B1]): Tree[A, B1] = { + if (isRedTree(l) && isRedTree(l.left)) + RedTree(l.key, l.value, BlackTree(l.left.key, l.left.value, l.left.left, l.left.right), BlackTree(z, zv, l.right, d)) + else if (isRedTree(l) && isRedTree(l.right)) + RedTree(l.right.key, l.right.value, BlackTree(l.key, l.value, l.left, l.right.left), BlackTree(z, zv, l.right.right, d)) + else + mkTree(isBlack, z, zv, l, d) + } + private[this] def balanceRight[A, B, B1 >: B](isBlack: Boolean, x: A, xv: B, a: Tree[A, B1], r: Tree[A, B1]): Tree[A, B1] = { + if (isRedTree(r) && isRedTree(r.left)) + RedTree(r.left.key, r.left.value, BlackTree(x, xv, a, r.left.left), BlackTree(r.key, r.value, r.left.right, r.right)) + else if (isRedTree(r) && isRedTree(r.right)) + RedTree(r.key, r.value, BlackTree(x, xv, a, r.left), BlackTree(r.right.key, r.right.value, r.right.left, r.right.right)) + else + mkTree(isBlack, x, xv, a, r) + } + private[this] def upd[A, B, B1 >: B](tree: Tree[A, B], k: A, v: B1, overwrite: Boolean)(implicit ordering: Ordering[A]): Tree[A, B1] = if (tree eq null) { + RedTree(k, v, null, null) + } else { + val cmp = ordering.compare(k, tree.key) + if (cmp < 0) balanceLeft(isBlackTree(tree), tree.key, tree.value, upd(tree.left, k, v, overwrite), tree.right) + else if (cmp > 0) balanceRight(isBlackTree(tree), tree.key, tree.value, tree.left, upd(tree.right, k, v, overwrite)) + else if (overwrite || k != tree.key) mkTree(isBlackTree(tree), k, v, tree.left, tree.right) + else tree + } + private[this] def updNth[A, B, B1 >: B](tree: Tree[A, B], idx: Int, k: A, v: B1, overwrite: Boolean): Tree[A, B1] = if (tree eq null) { + RedTree(k, v, null, null) + } else { + val rank = count(tree.left) + 1 + if (idx < rank) balanceLeft(isBlackTree(tree), tree.key, tree.value, updNth(tree.left, idx, k, v, overwrite), tree.right) + else if (idx > rank) balanceRight(isBlackTree(tree), tree.key, tree.value, tree.left, updNth(tree.right, idx - rank, k, v, overwrite)) + else if (overwrite) mkTree(isBlackTree(tree), k, v, tree.left, tree.right) + else tree + } + + /* Based on Stefan Kahrs' Haskell version of Okasaki's Red&Black Trees + * http://www.cse.unsw.edu.au/~dons/data/RedBlackTree.html */ + private[this] def del[A, B](tree: Tree[A, B], k: A)(implicit ordering: Ordering[A]): Tree[A, B] = if (tree eq null) null else { + def balance(x: A, xv: B, tl: Tree[A, B], tr: Tree[A, B]) = if (isRedTree(tl)) { + if (isRedTree(tr)) { + RedTree(x, xv, tl.black, tr.black) + } else if (isRedTree(tl.left)) { + RedTree(tl.key, tl.value, tl.left.black, BlackTree(x, xv, tl.right, tr)) + } else if (isRedTree(tl.right)) { + RedTree(tl.right.key, tl.right.value, BlackTree(tl.key, tl.value, tl.left, tl.right.left), BlackTree(x, xv, tl.right.right, tr)) + } else { + BlackTree(x, xv, tl, tr) + } + } else if (isRedTree(tr)) { + if (isRedTree(tr.right)) { + RedTree(tr.key, tr.value, BlackTree(x, xv, tl, tr.left), tr.right.black) + } else if (isRedTree(tr.left)) { + RedTree(tr.left.key, tr.left.value, BlackTree(x, xv, tl, tr.left.left), BlackTree(tr.key, tr.value, tr.left.right, tr.right)) + } else { + BlackTree(x, xv, tl, tr) + } + } else { + BlackTree(x, xv, tl, tr) + } + def subl(t: Tree[A, B]) = + if (t.isInstanceOf[BlackTree[_, _]]) t.red + else sys.error("Defect: invariance violation; expected black, got "+t) + + def balLeft(x: A, xv: B, tl: Tree[A, B], tr: Tree[A, B]) = if (isRedTree(tl)) { + RedTree(x, xv, tl.black, tr) + } else if (isBlackTree(tr)) { + balance(x, xv, tl, tr.red) + } else if (isRedTree(tr) && isBlackTree(tr.left)) { + RedTree(tr.left.key, tr.left.value, BlackTree(x, xv, tl, tr.left.left), balance(tr.key, tr.value, tr.left.right, subl(tr.right))) + } else { + sys.error("Defect: invariance violation") + } + def balRight(x: A, xv: B, tl: Tree[A, B], tr: Tree[A, B]) = if (isRedTree(tr)) { + RedTree(x, xv, tl, tr.black) + } else if (isBlackTree(tl)) { + balance(x, xv, tl.red, tr) + } else if (isRedTree(tl) && isBlackTree(tl.right)) { + RedTree(tl.right.key, tl.right.value, balance(tl.key, tl.value, subl(tl.left), tl.right.left), BlackTree(x, xv, tl.right.right, tr)) + } else { + sys.error("Defect: invariance violation") + } + def delLeft = if (isBlackTree(tree.left)) balLeft(tree.key, tree.value, del(tree.left, k), tree.right) else RedTree(tree.key, tree.value, del(tree.left, k), tree.right) + def delRight = if (isBlackTree(tree.right)) balRight(tree.key, tree.value, tree.left, del(tree.right, k)) else RedTree(tree.key, tree.value, tree.left, del(tree.right, k)) + def append(tl: Tree[A, B], tr: Tree[A, B]): Tree[A, B] = if (tl eq null) { + tr + } else if (tr eq null) { + tl + } else if (isRedTree(tl) && isRedTree(tr)) { + val bc = append(tl.right, tr.left) + if (isRedTree(bc)) { + RedTree(bc.key, bc.value, RedTree(tl.key, tl.value, tl.left, bc.left), RedTree(tr.key, tr.value, bc.right, tr.right)) + } else { + RedTree(tl.key, tl.value, tl.left, RedTree(tr.key, tr.value, bc, tr.right)) + } + } else if (isBlackTree(tl) && isBlackTree(tr)) { + val bc = append(tl.right, tr.left) + if (isRedTree(bc)) { + RedTree(bc.key, bc.value, BlackTree(tl.key, tl.value, tl.left, bc.left), BlackTree(tr.key, tr.value, bc.right, tr.right)) + } else { + balLeft(tl.key, tl.value, tl.left, BlackTree(tr.key, tr.value, bc, tr.right)) + } + } else if (isRedTree(tr)) { + RedTree(tr.key, tr.value, append(tl, tr.left), tr.right) + } else if (isRedTree(tl)) { + RedTree(tl.key, tl.value, tl.left, append(tl.right, tr)) + } else { + sys.error("unmatched tree on append: " + tl + ", " + tr) + } + + val cmp = ordering.compare(k, tree.key) + if (cmp < 0) delLeft + else if (cmp > 0) delRight + else append(tree.left, tree.right) + } + + private[this] def doFrom[A, B](tree: Tree[A, B], from: A)(implicit ordering: Ordering[A]): Tree[A, B] = { + if (tree eq null) return null + if (ordering.lt(tree.key, from)) return doFrom(tree.right, from) + val newLeft = doFrom(tree.left, from) + if (newLeft eq tree.left) tree + else if (newLeft eq null) upd(tree.right, tree.key, tree.value, overwrite = false) + else rebalance(tree, newLeft, tree.right) + } + private[this] def doTo[A, B](tree: Tree[A, B], to: A)(implicit ordering: Ordering[A]): Tree[A, B] = { + if (tree eq null) return null + if (ordering.lt(to, tree.key)) return doTo(tree.left, to) + val newRight = doTo(tree.right, to) + if (newRight eq tree.right) tree + else if (newRight eq null) upd(tree.left, tree.key, tree.value, overwrite = false) + else rebalance(tree, tree.left, newRight) + } + private[this] def doUntil[A, B](tree: Tree[A, B], until: A)(implicit ordering: Ordering[A]): Tree[A, B] = { + if (tree eq null) return null + if (ordering.lteq(until, tree.key)) return doUntil(tree.left, until) + val newRight = doUntil(tree.right, until) + if (newRight eq tree.right) tree + else if (newRight eq null) upd(tree.left, tree.key, tree.value, overwrite = false) + else rebalance(tree, tree.left, newRight) + } + private[this] def doRange[A, B](tree: Tree[A, B], from: A, until: A)(implicit ordering: Ordering[A]): Tree[A, B] = { + if (tree eq null) return null + if (ordering.lt(tree.key, from)) return doRange(tree.right, from, until) + if (ordering.lteq(until, tree.key)) return doRange(tree.left, from, until) + val newLeft = doFrom(tree.left, from) + val newRight = doUntil(tree.right, until) + if ((newLeft eq tree.left) && (newRight eq tree.right)) tree + else if (newLeft eq null) upd(newRight, tree.key, tree.value, overwrite = false) + else if (newRight eq null) upd(newLeft, tree.key, tree.value, overwrite = false) + else rebalance(tree, newLeft, newRight) + } + + private[this] def doDrop[A, B](tree: Tree[A, B], n: Int): Tree[A, B] = { + if (n <= 0) return tree + if (n >= this.count(tree)) return null + val count = this.count(tree.left) + if (n > count) return doDrop(tree.right, n - count - 1) + val newLeft = doDrop(tree.left, n) + if (newLeft eq tree.left) tree + else if (newLeft eq null) updNth(tree.right, n - count - 1, tree.key, tree.value, overwrite = false) + else rebalance(tree, newLeft, tree.right) + } + private[this] def doTake[A, B](tree: Tree[A, B], n: Int): Tree[A, B] = { + if (n <= 0) return null + if (n >= this.count(tree)) return tree + val count = this.count(tree.left) + if (n <= count) return doTake(tree.left, n) + val newRight = doTake(tree.right, n - count - 1) + if (newRight eq tree.right) tree + else if (newRight eq null) updNth(tree.left, n, tree.key, tree.value, overwrite = false) + else rebalance(tree, tree.left, newRight) + } + private[this] def doSlice[A, B](tree: Tree[A, B], from: Int, until: Int): Tree[A, B] = { + if (tree eq null) return null + val count = this.count(tree.left) + if (from > count) return doSlice(tree.right, from - count - 1, until - count - 1) + if (until <= count) return doSlice(tree.left, from, until) + val newLeft = doDrop(tree.left, from) + val newRight = doTake(tree.right, until - count - 1) + if ((newLeft eq tree.left) && (newRight eq tree.right)) tree + else if (newLeft eq null) updNth(newRight, from - count - 1, tree.key, tree.value, overwrite = false) + else if (newRight eq null) updNth(newLeft, until, tree.key, tree.value, overwrite = false) + else rebalance(tree, newLeft, newRight) + } + + // The zipper returned might have been traversed left-most (always the left child) + // or right-most (always the right child). Left trees are traversed right-most, + // and right trees are traversed leftmost. + + // Returns the zipper for the side with deepest black nodes depth, a flag + // indicating whether the trees were unbalanced at all, and a flag indicating + // whether the zipper was traversed left-most or right-most. + + // If the trees were balanced, returns an empty zipper + private[this] def compareDepth[A, B](left: Tree[A, B], right: Tree[A, B]): (NList[Tree[A, B]], Boolean, Boolean, Int) = { + import NList.cons + // Once a side is found to be deeper, unzip it to the bottom + def unzip(zipper: NList[Tree[A, B]], leftMost: Boolean): NList[Tree[A, B]] = { + val next = if (leftMost) zipper.head.left else zipper.head.right + if (next eq null) zipper + else unzip(cons(next, zipper), leftMost) + } + + // Unzip left tree on the rightmost side and right tree on the leftmost side until one is + // found to be deeper, or the bottom is reached + def unzipBoth(left: Tree[A, B], + right: Tree[A, B], + leftZipper: NList[Tree[A, B]], + rightZipper: NList[Tree[A, B]], + smallerDepth: Int): (NList[Tree[A, B]], Boolean, Boolean, Int) = { + if (isBlackTree(left) && isBlackTree(right)) { + unzipBoth(left.right, right.left, cons(left, leftZipper), cons(right, rightZipper), smallerDepth + 1) + } else if (isRedTree(left) && isRedTree(right)) { + unzipBoth(left.right, right.left, cons(left, leftZipper), cons(right, rightZipper), smallerDepth) + } else if (isRedTree(right)) { + unzipBoth(left, right.left, leftZipper, cons(right, rightZipper), smallerDepth) + } else if (isRedTree(left)) { + unzipBoth(left.right, right, cons(left, leftZipper), rightZipper, smallerDepth) + } else if ((left eq null) && (right eq null)) { + (null, true, false, smallerDepth) + } else if ((left eq null) && isBlackTree(right)) { + val leftMost = true + (unzip(cons(right, rightZipper), leftMost), false, leftMost, smallerDepth) + } else if (isBlackTree(left) && (right eq null)) { + val leftMost = false + (unzip(cons(left, leftZipper), leftMost), false, leftMost, smallerDepth) + } else { + sys.error("unmatched trees in unzip: " + left + ", " + right) + } + } + unzipBoth(left, right, null, null, 0) + } + + private[this] def rebalance[A, B](tree: Tree[A, B], newLeft: Tree[A, B], newRight: Tree[A, B]) = { + // This is like drop(n-1), but only counting black nodes + @tailrec + def findDepth(zipper: NList[Tree[A, B]], depth: Int): NList[Tree[A, B]] = + if (zipper eq null) { + sys.error("Defect: unexpected empty zipper while computing range") + } else if (isBlackTree(zipper.head)) { + if (depth == 1) zipper else findDepth(zipper.tail, depth - 1) + } else { + findDepth(zipper.tail, depth) + } + + // Blackening the smaller tree avoids balancing problems on union; + // this can't be done later, though, or it would change the result of compareDepth + val blkNewLeft = blacken(newLeft) + val blkNewRight = blacken(newRight) + val (zipper, levelled, leftMost, smallerDepth) = compareDepth(blkNewLeft, blkNewRight) + + if (levelled) { + BlackTree(tree.key, tree.value, blkNewLeft, blkNewRight) + } else { + val zipFrom = findDepth(zipper, smallerDepth) + val union = if (leftMost) { + RedTree(tree.key, tree.value, blkNewLeft, zipFrom.head) + } else { + RedTree(tree.key, tree.value, zipFrom.head, blkNewRight) + } + val zippedTree = NList.foldLeft(zipFrom.tail, union: Tree[A, B]) { (tree, node) => + if (leftMost) + balanceLeft(isBlackTree(node), node.key, node.value, tree, node.right) + else + balanceRight(isBlackTree(node), node.key, node.value, node.left, tree) + } + zippedTree + } + } + + // Null optimized list implementation for tree rebalancing. null presents Nil. + private[this] final class NList[A](val head: A, val tail: NList[A]) + + private[this] final object NList { + + def cons[B](x: B, xs: NList[B]): NList[B] = new NList(x, xs) + + def foldLeft[A, B](xs: NList[A], z: B)(f: (B, A) => B): B = { + var acc = z + var these = xs + while (these ne null) { + acc = f(acc, these.head) + these = these.tail + } + acc + } + + } + + /* + * Forcing direct fields access using the @inline annotation helps speed up + * various operations (especially smallest/greatest and update/delete). + * + * Unfortunately the direct field access is not guaranteed to work (but + * works on the current implementation of the Scala compiler). + * + * An alternative is to implement the these classes using plain old Java code... + */ + sealed abstract class Tree[A, +B]( + @(inline @getter) final val key: A, + @(inline @getter) final val value: B, + @(inline @getter) final val left: Tree[A, B], + @(inline @getter) final val right: Tree[A, B]) + extends Serializable { + @(inline @getter) final val count: Int = 1 + RedBlackTree.count(left) + RedBlackTree.count(right) + def black: Tree[A, B] + def red: Tree[A, B] + } + final class RedTree[A, +B](key: A, + value: B, + left: Tree[A, B], + right: Tree[A, B]) extends Tree[A, B](key, value, left, right) { + override def black: Tree[A, B] = BlackTree(key, value, left, right) + override def red: Tree[A, B] = this + override def toString: String = "RedTree(" + key + ", " + value + ", " + left + ", " + right + ")" + } + final class BlackTree[A, +B](key: A, + value: B, + left: Tree[A, B], + right: Tree[A, B]) extends Tree[A, B](key, value, left, right) { + override def black: Tree[A, B] = this + override def red: Tree[A, B] = RedTree(key, value, left, right) + override def toString: String = "BlackTree(" + key + ", " + value + ", " + left + ", " + right + ")" + } + + object RedTree { + @inline def apply[A, B](key: A, value: B, left: Tree[A, B], right: Tree[A, B]) = new RedTree(key, value, left, right) + def unapply[A, B](t: RedTree[A, B]) = Some((t.key, t.value, t.left, t.right)) + } + object BlackTree { + @inline def apply[A, B](key: A, value: B, left: Tree[A, B], right: Tree[A, B]) = new BlackTree(key, value, left, right) + def unapply[A, B](t: BlackTree[A, B]) = Some((t.key, t.value, t.left, t.right)) + } + + private[this] abstract class TreeIterator[A, B, R](root: Tree[A, B], start: Option[A])(implicit ordering: Ordering[A]) extends Iterator[R] { + protected[this] def nextResult(tree: Tree[A, B]): R + + override def hasNext: Boolean = lookahead ne null + + override def next: R = lookahead match { + case null => + throw new NoSuchElementException("next on empty iterator") + case tree => + lookahead = findLeftMostOrPopOnEmpty(goRight(tree)) + nextResult(tree) + } + +// @tailrec + private[this] def findLeftMostOrPopOnEmpty(tree: Tree[A, B]): Tree[A, B] = + if (tree eq null) popNext() + else if (tree.left eq null) tree + else findLeftMostOrPopOnEmpty(goLeft(tree)) + + private[this] def pushNext(tree: Tree[A, B]): Unit = { + try { + stackOfNexts(index) = tree + index += 1 + } catch { + case _: ArrayIndexOutOfBoundsException => + /* + * Either the tree became unbalanced or we calculated the maximum height incorrectly. + * To avoid crashing the iterator we expand the path array. Obviously this should never + * happen... + * + * An exception handler is used instead of an if-condition to optimize the normal path. + * This makes a large difference in iteration speed! + */ + assert(index >= stackOfNexts.length) + stackOfNexts :+= null + pushNext(tree) + } + } + private[this] def popNext(): Tree[A, B] = if (index == 0) null else { + index -= 1 + stackOfNexts(index) + } + + private[this] var stackOfNexts = if (root eq null) null else { + /* + * According to "Ralf Hinze. Constructing red-black trees" [http://www.cs.ox.ac.uk/ralf.hinze/publications/#P5] + * the maximum height of a red-black tree is 2*log_2(n + 2) - 2. + * + * According to {@see Integer#numberOfLeadingZeros} ceil(log_2(n)) = (32 - Integer.numberOfLeadingZeros(n - 1)) + * + * We also don't store the deepest nodes in the path so the maximum path length is further reduced by one. + */ + val maximumHeight = 2 * (32 - Integer.numberOfLeadingZeros(root.count + 2 - 1)) - 2 - 1 + new Array[Tree[A, B]](maximumHeight) + } + private[this] var index = 0 + private[this] var lookahead: Tree[A, B] = start map startFrom getOrElse findLeftMostOrPopOnEmpty(root) + + /** + * Find the leftmost subtree whose key is equal to the given key, or if no such thing, + * the leftmost subtree with the key that would be "next" after it according + * to the ordering. Along the way build up the iterator's path stack so that "next" + * functionality works. + */ + private[this] def startFrom(key: A) : Tree[A,B] = if (root eq null) null else { + @tailrec def find(tree: Tree[A, B]): Tree[A, B] = + if (tree eq null) popNext() + else find( + if (ordering.lteq(key, tree.key)) goLeft(tree) + else goRight(tree) + ) + find(root) + } + + private[this] def goLeft(tree: Tree[A, B]) = { + pushNext(tree) + tree.left + } + + private[this] def goRight(tree: Tree[A, B]) = tree.right + } + + private[this] class EntriesIterator[A: Ordering, B](tree: Tree[A, B], focus: Option[A]) extends TreeIterator[A, B, (A, B)](tree, focus) { + override def nextResult(tree: Tree[A, B]) = (tree.key, tree.value) + } + + private[this] class KeysIterator[A: Ordering, B](tree: Tree[A, B], focus: Option[A]) extends TreeIterator[A, B, A](tree, focus) { + override def nextResult(tree: Tree[A, B]) = tree.key + } + + private[this] class ValuesIterator[A: Ordering, B](tree: Tree[A, B], focus: Option[A]) extends TreeIterator[A, B, B](tree, focus) { + override def nextResult(tree: Tree[A, B]) = tree.value + } +} + +object Test { + def main(args: Array[String]) = {} +} |