function testFlags(validity, flags) {
  var i, flag;
  if (flags) {
    for (i=0; i<flags.length; ++i) {
      flag = flags[i];
      if (validity[flag]) {
        return true;
      }
    }
  }
  return false;
}
@ngdoc input
@name input[checkbox]

@description
HTML checkbox.

@param {string} ngModel Assignable angular expression to data-bind to.
@param {string=} name Property name of the form under which the control is published.
@param {string=} ngTrueValue The value to which the expression should be set when selected.
@param {string=} ngFalseValue The value to which the expression should be set when not selected.
@param {string=} ngChange Angular expression to be executed when input changes due to user
   interaction with the input element.

@example
      <example name="checkbox-input-directive" module="checkboxExample">
        <file name="index.html">
         <script>
           angular.module('checkboxExample', [])
             .controller('ExampleController', ['$scope', function($scope) {
               $scope.value1 = true;
               $scope.value2 = 'YES'
             }]);
         </script>
         <form name="myForm" ng-controller="ExampleController">
           Value1: <input type="checkbox" ng-model="value1"> <br/>
           Value2: <input type="checkbox" ng-model="value2"
                          ng-true-value="YES" ng-false-value="NO"> <br/>
           <tt>value1 = {{value1}}</tt><br/>
           <tt>value2 = {{value2}}</tt><br/>
          </form>
        </file>
        <file name="protractor.js" type="protractor">
          it('should change state', function() {
            var value1 = element(by.binding('value1'));
            var value2 = element(by.binding('value2'));

            expect(value1.getText()).toContain('true');
            expect(value2.getText()).toContain('YES');

            element(by.model('value1')).click();
            element(by.model('value2')).click();

            expect(value1.getText()).toContain('false');
            expect(value2.getText()).toContain('NO');
          });
        </file>
      </example>