void animationDirection() throws ScriptException {
		checkStatementLength(4);
		boolean negative = false;
		if (statement[2].tok == Token.hyphen)
			negative = true;
		else if (statement[2].tok != Token.plus)
			invalidArgument();
		if (statement[3].tok != Token.integer)
			invalidArgument();
		int direction = statement[3].intValue;
		if (direction != 1)
			numberMustBe(-1, 1);
		if (negative)
			direction = -direction;
		viewer.setAnimationDirection(direction);
	}