text: // This is a constructor function that initializes new Range objects.
  // Note that it does not create or return the object. It just initializes this.
  function Range(from, to) {
      // Store the start and end points (state) of this new range object.
      // These are noninherited properties that are unique to this object.
      this.from = from;
      this.to = to;
  }
  
  // All Range objects inherit from this object.
  // Note that the property name must be "prototype" for this to work.
  Range.prototype = {
      // Return true if x is in the range, false otherwise
      // This method works for textual and Date ranges as well as numeric.
      includes: function(x) { return this.from <= x && x <= this.to; },
  
      // A generator function that makes instances of the class iterable.
      // Note that it only works for numeric ranges.
      [Symbol.iterator]: function*() {
          for(let x = Math.ceil(this.from); x <= this.to; x++) yield x;
      },
  
      // Return a string representation of the range
      toString: function() { return "(" + this.from + "..." + this.to + ")"; }
  };
  