From ec608257af69e4865de7d79c7c88e4ab7710407a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ali=20Sinan=20K=C3=B6ksal?= <alisinan@gmail.com>
Date: Tue, 8 Nov 2011 05:54:36 +0000
Subject: [PATCH] Random generation of red-black trees using ScalaCheck
---
scalacheck-testcases/.RedBlackTree.scala.swp | Bin 0 -> 12288 bytes
scalacheck-testcases/RedBlackTree.scala | 115 +++++++++++++++++++
2 files changed, 115 insertions(+)
create mode 100644 scalacheck-testcases/.RedBlackTree.scala.swp
create mode 100644 scalacheck-testcases/RedBlackTree.scala
diff --git a/scalacheck-testcases/.RedBlackTree.scala.swp b/scalacheck-testcases/.RedBlackTree.scala.swp
new file mode 100644
index 0000000000000000000000000000000000000000..2e890afaec248d96d8ac36518b0a45c8241f7317
GIT binary patch
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diff --git a/scalacheck-testcases/RedBlackTree.scala b/scalacheck-testcases/RedBlackTree.scala
new file mode 100644
index 000000000..30bbb9222
--- /dev/null
+++ b/scalacheck-testcases/RedBlackTree.scala
@@ -0,0 +1,115 @@
+import org.scalacheck._
+import Gen._
+import Arbitrary.arbitrary
+
+object Specs {
+ sealed abstract class Color
+ case class Red() extends Color
+ case class Black() extends Color
+
+ sealed abstract class Tree
+ case class Empty() extends Tree
+ case class Node(color: Color, left: Tree, value: Int, right: Tree) extends Tree
+
+ sealed abstract class OptionInt
+ case class SomeInt(v : Int) extends OptionInt
+ case class NoneInt() extends OptionInt
+
+ def max(a: Int, b: Int) : Int = {
+ if (a >= b) a else b
+ } ensuring (res => res >= a && res >= b)
+
+ def size(t: Tree) : Int = (t match {
+ case Empty() => 0
+ case Node(_, l, v, r) => size(l) + 1 + size(r)
+ }) ensuring (_ >= 0)
+
+ def height(t: Tree) : Int = (t match {
+ case Empty() => 0
+ case Node(_,l,_,r) => max(height(l), height(r)) + 1
+ }) ensuring (_ >= 0)
+
+ def isBlack(t: Tree) : Boolean = t match {
+ case Empty() => true
+ case Node(Black(),_,_,_) => true
+ case _ => false
+ }
+
+ def redNodesHaveBlackChildren(t: Tree) : Boolean = t match {
+ case Empty() => true
+ case Node(Black(), l, _, r) => redNodesHaveBlackChildren(l) && redNodesHaveBlackChildren(r)
+ case Node(Red(), l, _, r) => isBlack(l) && isBlack(r) && redNodesHaveBlackChildren(l) && redNodesHaveBlackChildren(r)
+ }
+
+ def blackBalanced(t : Tree) : Boolean = t match {
+ case Node(_,l,_,r) => blackBalanced(l) && blackBalanced(r) && blackHeight(l) == blackHeight(r)
+ case Empty() => true
+ }
+
+ def blackHeight(t : Tree) : Int = t match {
+ case Empty() => 0
+ case Node(Black(), l, _, _) => blackHeight(l) + 1
+ case Node(Red(), l, _, _) => blackHeight(l)
+ }
+
+ def valuesWithin(t : Tree, bound : Int) : Boolean = t match {
+ case Empty() => true
+ case Node(_,l,v,r) => 0 <= v && v <= bound && valuesWithin(l,bound) && valuesWithin(r,bound)
+ }
+
+ def orderedKeys(t : Tree) : Boolean = orderedKeys(t, NoneInt(), NoneInt())
+
+ def orderedKeys(t : Tree, min : OptionInt, max : OptionInt) : Boolean = t match {
+ case Empty() => true
+ case Node(c,a,v,b) =>
+ val minOK =
+ min match {
+ case SomeInt(minVal) =>
+ v > minVal
+ case NoneInt() => true
+ }
+ val maxOK =
+ max match {
+ case SomeInt(maxVal) =>
+ v < maxVal
+ case NoneInt() => true
+ }
+ minOK && maxOK && orderedKeys(a, min, SomeInt(v)) && orderedKeys(b, SomeInt(v), max)
+ }
+
+ def isRedBlackTree(t : Tree) : Boolean = {
+ blackBalanced(t) && redNodesHaveBlackChildren(t) && orderedKeys(t) // && isBlack(t)
+ }
+}
+object RedBlackTree {
+ import Specs._
+
+ val genLeaf = value(Empty())
+
+ def genColor: Gen[Color] = oneOf(Black(), Red())
+
+ val genNode = for {
+ v <- Gen.choose(1, 10)
+ left <- genTree
+ right <- genTree
+ color <- genColor
+ } yield Node(color, left, v, right)
+
+ def genTree: Gen[Tree] = oneOf(genLeaf, genNode)
+
+ def main(args: Array[String]): Unit = {
+ val iter = (new Iterator[Tree] {
+ private var counter = 0
+ def hasNext : Boolean = true || counter < 10
+ def next : Tree = { counter += 1; genTree.sample.get }
+ })
+
+ val s = scala.collection.mutable.Set[Int]()
+
+ for (t <- iter if isRedBlackTree(t)) {
+ //println("Here is a tree : " + t)
+ s += (size(t))
+ println(s)
+ }
+ }
+}
--
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