add more enum exhaustivity tests

Author: liufengyun

tests/patmat/enum-HList.scala

@@ -0,0 +1,22 @@
+enum HLst {
+  case HCons[+Hd, +Tl <: HLst](hd: Hd, tl: Tl)
+  case HNil
+}
+
+object Test {
+  import HLst._
+  def length(hl: HLst): Int = hl match {
+    case HCons(_, tl) => 1 + length(tl)
+    case HNil => 0
+  }
+  def sumInts(hl: HLst): Int = hl match {
+    case HCons(x: Int, tl) => x + sumInts(tl)
+    case HCons(_, tl) => sumInts(tl)
+    case HNil => 0
+  }
+  def main(args: Array[String]) = {
+    val hl = HCons(1, HCons("A", HNil))
+    assert(length(hl) == 2, length(hl))
+    assert(sumInts(hl) == 1)
+  }
+}

tests/patmat/enum-Tree.scala

@@ -0,0 +1,29 @@
+enum Tree[T] {
+  case True extends Tree[Boolean]
+  case False extends Tree[Boolean]
+  case Zero extends Tree[Int]
+  case Succ(n: Tree[Int]) extends Tree[Int]
+  case Pred(n: Tree[Int]) extends Tree[Int]
+  case IsZero(n: Tree[Int]) extends Tree[Boolean]
+  case If(cond: Tree[Boolean], thenp: Tree[T], elsep: Tree[T])
+}
+
+object Test {
+  import Tree._
+
+  def eval[T](e: Tree[T]): T = e match {
+    case True => true
+    case False => false
+    case Zero => 0
+    case Succ(f) => eval(f) + 1
+    case Pred(f) => eval(f) - 1
+    case IsZero(f) => eval(f) == 0
+    case If(cond, thenp, elsep) => if (eval(cond)) eval(thenp) else eval(elsep)
+  }
+
+  val data = If(IsZero(Pred(Succ(Zero))), Succ(Succ(Zero)), Pred(Pred(Zero)))
+
+  def main(args: Array[String]) = {
+    println(s"$data --> ${eval(data)}")
+  }
+}

tests/patmat/planets.scala

@@ -0,0 +1,26 @@
+enum class Planet(mass: Double, radius: Double) {
+  private final val G = 6.67300E-11
+  def surfaceGravity = G * mass / (radius * radius)
+  def surfaceWeight(otherMass: Double) =  otherMass * surfaceGravity
+}
+object Planet {
+  case MERCURY extends Planet(3.303e+23, 2.4397e6)
+  case VENUS   extends Planet(4.869e+24, 6.0518e6)
+  case EARTH   extends Planet(5.976e+24, 6.37814e6)
+  case MARS    extends Planet(6.421e+23, 3.3972e6)
+  case JUPITER extends Planet(1.9e+27,   7.1492e7)
+  case SATURN  extends Planet(5.688e+26, 6.0268e7)
+  case URANUS  extends Planet(8.686e+25, 2.5559e7)
+  case NEPTUNE extends Planet(1.024e+26, 2.4746e7)
+}
+object Test {
+  def main(args: Array[String]) = {
+    import Planet._
+    assert(enumValueNamed("SATURN") == SATURN)
+    assert(enumValue(2) == EARTH)
+    val earthWeight = 100
+    val mass = earthWeight/EARTH.surfaceGravity
+    for (p <- enumValues)
+      println(s"Your weight on $p is ${p.surfaceWeight(mass)}")
+  }
+}