title: When would you surround routerLink in square brackets?
body: <p>The Angular 2 <a href="https://angular.io/docs/ts/latest/guide/cheatsheet.html" rel="noreferrer">cheat sheet</a> shows examples of <code>routerLink</code> both with and without square brackets in templates:</p>
  
  <pre><code>&lt;a routerLink="/path"&gt;
  &lt;a [routerLink]="[ '/path', routeParam ]"&gt;
  &lt;a [routerLink]="[ '/path', { matrixParam: 'value' } ]"&gt;
  &lt;a [routerLink]="[ '/path' ]" [queryParams]="{ page: 1 }"&gt;
  &lt;a [routerLink]="[ '/path' ]" fragment="anchor"&gt;
  </code></pre>
  
  <p>What's the difference in functionality?</p>