expressions-increment-operator.html

<!DOCTYPE html>
<html>
<head>
  <script data-require="angular.js@1.4.8" data-semver="1.4.8" src="https://cdnjs.cloudflare.com/ajax/libs/angular.js/1.4.8/angular.min.js"></script>
</head>
<body ng-app>
  {{variable = 5; ++variable}}
</body>
</html>

http://blog.allii.ir/2016/01/angularjs-begineer-intermediate-course-basics-part-one/#expressions