title: Why the reselect createSelector necessary in this @ngrx example?
body: <p>What does the following code snippet do? It is taken from this <a href="https://github.com/ngrx/example-app/blob/master/src/app/reducers/index.ts" rel="noreferrer">file</a>.</p>
  
  <p><code>export const getCollectionLoading = createSelector(getCollectionState, fromCollection.getLoading);</code></p>
  
  <p>The <code>fromCollection.getLoading</code> has only either <code>true</code> or <code>false</code> value, so can there be any optimization achieved by using the <code>createSelector</code>? </p>
  
  <p>in</p>
  
  <pre><code>export const getCollectionLoaded = createSelector(getCollectionState, fromCollection.getLoaded);
  
  export const getCollectionLoading = createSelector(getCollectionState, fromCollection.getLoading);
  
  export const getCollectionBookIds = createSelector(getCollectionState, fromCollection.getIds);
  </code></pre>