Point3f atomCenterOrCoordinateParameter(int i) throws ScriptException {
		if (i >= statementLength)
			badArgumentCount();
		switch (statement[i].tok) {
		case Token.expressionBegin:
			return viewer.getAtomSetCenter(expression(statement, ++i));
		case Token.leftbrace:
			return getCoordinate(i, true);
		}
		invalidArgument();
		// impossible return
		return null;
	}