code: function(pos) {
          var x = this.x, y = this.y;
          this.x = x*pos.x - y*pos.y;
          this.y = y*pos.x + x*pos.y;
          return this;
      }
docs: /*
  Method: $prod
  
  Returns the result of multiplying two <Complex> numbers.
  
  Alters the original object.
  
  Parameters:
  
  pos - A <Complex> instance.
  
  Returns:
  
  The result of multiplying two complex numbers.