How to get a type of scope variable in Angular expression?

Let's define simple boolean on the scope:

var mymodal = angular.module('mymodal', []);

mymodal.controller('MainCtrl', function ($scope) {
    $scope.b = false;
});

How can I get type of a variable in the expression? typeOf and Object.prototype.Tostring.call don't work.

<div ng-controller="MainCtrl" class="container">
        <div>
          {{ b }}
          {{ typeOf(b) }}
          {{ Object.prototype.toString.call(b) }}
        </div>
</div>

Here's JSFiddle: http://jsfiddle.net/g8Ld80x3/2/