Data commit

Task/Stack/Scala/stack-1.scala

@@ -0,0 +1,17 @@
+class Stack[T] {
+  private var items = List[T]()
+
+  def isEmpty = items.isEmpty
+
+  def peek = items match {
+    case List()       => error("Stack empty")
+    case head :: rest => head
+  }
+
+  def pop = items match {
+    case List()       => error("Stack empty")
+    case head :: rest => items = rest; head
+  }
+
+  def push(value: T) = items = value +: items
+}

Task/Stack/Scala/stack-2.scala

@@ -0,0 +1,9 @@
+import collection.mutable.{ Stack => Stak }
+
+class Stack[T] extends Stak[T] {
+  override def pop: T = {
+    if (this.length == 0) error("Can't Pop from an empty Stack.")
+    else super.pop
+  }
+  def peek: T = this.head
+}

Task/Stack/Scala/stack-3.scala

@@ -0,0 +1,13 @@
+object StackTest extends App {
+
+  val stack = new Stack[String]
+
+  stack.push("Peter Pan")
+  stack.push("Suske & Wiske", "Alice in Wonderland")
+
+  assert(stack.peek == "Alice in Wonderland")
+  assert(stack.pop() == "Alice in Wonderland")
+  assert(stack.pop() == "Suske & Wiske")
+  assert(stack.pop() == "Peter Pan")
+  println("Completed without errors")
+}