title: Vala - Constant Initialization and Assignment in Object Constructor
body: <p>I've been looking at the Vala programming language over the past few days, and it looks promising. However, I can't figure out how to properly assign a constant (currently the Vala equivalent to <code>final</code>) in object construction. For example, in Java:</p>
  
  <pre><code>import java.lang.Math;
  
  public class Rectangle {
      public final double sideA;
      public final double sideB;
      public final double area;
      public final double diagonal;
  
      public Rectangle (double SideA, double SideB) {
          sideA = SideA;
          sideB = SideB;
          area = SideA * SideB;
          diagonal = Math.sqrt(Math.pow(SideA, 2) + Math.pow(SideB, 2));
      }
  }
  </code></pre>
  
  <p>How would this be written in Vala?</p>