And - Manual

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  firstComputed: 0,
  secondComputed: 0,
  first: function() {
    this.incrementProperty('firstComputed');
    return false;
  }.property(),
  second: function() {
    this.incrementProperty('secondComputed');
    return true;
  }.property(),
  manualAnd: function() {
    return this.get('first') && this.get('second');
  }.property('first', 'second')
});

templates.application.hbs

<h1>And - Manual</h1>

<p>Value of manualAnd: {{manualAnd}}</p>
<p>Number of times first computed: {{firstComputed}}</p>
<p>Number of times second computed: {{secondComputed}}</p>

twiddle.json

{
  "version": "0.7.2",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.4.4/ember.debug.js",
    "ember-data": "https://cdnjs.cloudflare.com/ajax/libs/ember-data.js/2.4.3/ember-data.js",
    "ember-template-compiler": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.4.4/ember-template-compiler.js"
  }
}