bootstrap 4 pull-right无效

/**********************************************************************

 *                   bootstrap 4 pull-right无效

 * 说明：

 *     在测试bootstrap的时候发现pull-right无效，原来是已经换成了float-right。

 *

 *                                2018-4-25 深圳 宝安西乡 曾剑锋

 *********************************************************************/

一、参考文档：

    . What happened to the .pull-left and .pull-right classes in Bootstrap ?

        https://stackoverflow.com/questions/39655110/what-happened-to-the-pull-left-and-pull-right-classes-in-bootstrap-4

    . pull-right replacement in bootstrap  does not work

        https://stackoverflow.com/questions/46221635/pull-right-replacement-in-bootstrap-4-does-not-work

二、解决办法：

    The classes are currently float-right float-sm-right etc.