code: function() {
  
  		this._active_argument_index = -1;
  
  		for (var i = 0; i < this._count_arguments; i++) {
  
  			if (!!this._arguments[i].getValue()) {
  
  				this._active_argument_index = i;
  				break;
  
  			}
  
  		}
  
  	}
docs: Get index of the first argument which evaluates to <kw>true</kw>
  @returns {?number} Zero-based argument index, or <kw>null</kw>, if all arguments evaluate to <kw>false</kw>