title: angular js - condition in select "comprehension expression"
body: <p>i've got an angular app that maps one set of objects to another set of objects via two select elements.<br>
  when a mapping is made, the mapped objects' "mapped" property gets set to true.</p>
  
  <pre><code>&lt;select ng-model='sourceToMap' required='true' ng-options='code.code for code in sourceCodes'&gt;
  &lt;select ng-model='targetToMap' required='true' ng-options='code.code for code in targetCodes'&gt;&lt;/select&gt;
  </code></pre>
  
  <p>i'd like my select to show all the items in sourceCodes/targetCodes whose mapped property is false.  something like...</p>
  
  <pre><code>ng-options="code.code for code in sourceCodes where code.mapped = false"
  </code></pre>
  
  <p>if possible, i'd like to avoid having a mappedItems / unmappedItems collection cause that seems really gross</p>