Instantly share code, notes, and snippets.

# wh5a/QuickCheck.scala

Created November 10, 2013 05:09
Show Gist options
• Save wh5a/7394082 to your computer and use it in GitHub Desktop.
Coursera Reactive Scala Programming #1 - Quickcheck
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters. Learn more about bidirectional Unicode characters
 package quickcheck import common._ import org.scalacheck._ import Arbitrary._ import Gen._ import Prop._ import Math._ abstract class QuickCheckHeap extends Properties("Heap") with IntHeap { lazy val genHeap: Gen[H] = for { n <- arbitrary[A] h <- frequency((1, value(empty)), (9, genHeap)) } yield insert(n, h) property("hint1") = forAll { (n1: A, n2: A) => val h = insert(n1, insert(n2, empty)) findMin(h) == min(n1, n2) } property("hint2") = forAll { (n: A) => isEmpty(deleteMin(insert(n, empty))) } property("hint3") = forAll { (h: H) => def isSorted(h: H): Boolean = if (isEmpty(h)) true else { val m = findMin(h) val h2 = deleteMin(h) isEmpty(h2) || (m <= findMin(h2) && isSorted(h2)) } isSorted(h) } property("hint4") = forAll { (h1: H, h2: H) => findMin(meld(h1, h2)) == min(findMin(h1), findMin(h2)) } /* https://class.coursera.org/reactive-001/forum/thread?thread_id=97#post-371 */ property("meld") = forAll { (h1: H, h2: H) => def heapEqual(h1: H, h2: H): Boolean = if (isEmpty(h1) && isEmpty(h2)) true else { val m1 = findMin(h1) val m2 = findMin(h2) m1 == m2 && heapEqual(deleteMin(h1), deleteMin(h2)) } heapEqual(meld(h1, h2), meld(deleteMin(h1), insert(findMin(h1), h2))) } implicit lazy val arbHeap: Arbitrary[H] = Arbitrary(genHeap) }

### brett-shwom commented Jun 29, 2014

this came in handy, thanks!

### lucaslabs commented Apr 16, 2015

Hi @wh5a, I've tried this gist in Eclipse and the code is not compiling.

The `value(empty)` in the `genHeap` function is causing the error.

Any help?

### hveiga commented Apr 17, 2015

Gen.const(empty) for ScalaCheck 1.12.1

### lucaslabs commented Apr 17, 2015

That works @hveiga. Thanks for the help ✌️

### BeachBird commented Apr 25, 2015

One more property is missed for 10/10 Points :)
property("nw1") = forAll { (h1: H, h2: H) =>
val m1 = findMin(h1)
val m2 = findMin(h2)
val min = m1.min(m2)
findMin(meld(deleteMin(h1),insert(min,h2)))==min
}

@hveiga cheers!