Just another update

Task/Flow-control-structures/00DESCRIPTION

@@ -1,2 +1,5 @@
 {{Control Structures}}
-In this task, we document common flow-control structures. One common example of a flow-control structure is the <tt>goto</tt> construct. Note that [[Conditional Structures]] and [[Iteration|Loop Structures]] have their own articles/categories.
+In this task, we document common flow-control structures.
+One common example of a flow-control structure is the <tt>goto</tt> construct.
+Note that [[Conditional Structures]] and [[Iteration|Loop Structures]]
+have their own articles/categories.

Task/Flow-control-structures/Scala/flow-control-structures.scala

@@ -0,0 +1,26 @@
+import Goto._
+import scala.util.continuations._
+
+object Goto {
+
+  case class Label(k: Label => Unit)
+
+  private case class GotoThunk(label: Label) extends Throwable
+
+  def label: Label @suspendable =
+    shift((k: Label => Unit) => executeFrom(Label(k)))
+
+  def goto(l: Label): Nothing =
+    throw new GotoThunk(l)
+
+  private def executeFrom(label: Label): Unit = {
+    val nextLabel = try {
+      label.k(label)
+      None
+    } catch {
+      case g: GotoThunk => Some(g.label)
+    }
+    if (nextLabel.isDefined) executeFrom(nextLabel.get)
+  }
+
+}