angularJs 动态禁用启用a标签的 ng-click 怎么做

 <a href="javascript:void(0);"  ng-click="{{dis!=hasReg.cardNo?true:false}} || withdrawalNum()">退号</a>

a标签在ng-repeat中
我想让后面表达式匹配成功启用ng-click 功能，不匹配 禁用ng-click
可是这么写，总是禁用状态，哪怕匹配到false 也触发不了ng-click
求高手支招

<a href="javascript:void(0)"  ng-click="dis!=hasReg.cardNo?withdrawalNum():''" >
退号</a>