sbt/tasks/src/test/scala/TestRunnerSort.scala

import xsbt._

import org.scalacheck._
import Prop._
import TaskGen._

object TaskRunnerSortTest extends Properties("TaskRunnerSort")
{
	property("sort") = forAll(TaskListGen, MaxWorkersGen) { (list: List[Int], workers: Int) =>
		val a = list.toArray
		val sorted = a.toArray
		java.util.Arrays.sort(sorted)
		("Workers: " + workers) |: ("Array: " + a.toList) |:
		{
			def result = TaskRunner( sort(a.toArray), if(workers > 0) workers else 1)
			checkResult(result.toList, sorted.toList)
		}
	}
	final def sortDirect(a: RandomAccessSeq[Int]): RandomAccessSeq[Int] =
	{
		if(a.length < 2)
			a
		else
		{
			val pivot = a(0)
			val (lt,gte) = a.projection.drop(1).partition(_ < pivot)
			sortDirect(lt) ++ List(pivot) ++ sortDirect(gte)
		}
	}
	final def sort(a: RandomAccessSeq[Int]): Task[RandomAccessSeq[Int]] =
	{
		if(a.length < 200)
			Task(sortDirect(a))
		else
		{
			Task(a) bind { a =>
				val pivot = a(0)
				val (lt,gte) = a.projection.drop(1).partition(_ < pivot)
				(sort(lt), sort(gte)) map { _ ++ List(pivot) ++ _ }
			}
		}
	}
}