title: r unlist function unexpected results
body: <p>Trying to flatten a list to a vector I've just found an unexpected behaviour. To simplify let's do what <code>?unlist</code> proposes as an example:</p>
  
  <pre><code>unlist(options())
  </code></pre>
  
  <p>Look at the original list size:</p>
  
  <pre><code>length(unlist(options())) # 69 in my environment
  </code></pre>
  
  <p>Should the unlisted list retain its length? I would think so, but...</p>
  
  <pre><code>length(unlist(options())) # 79!!!
  length(unlist(options(), use.names = F)) # Another 79
  </code></pre>
  
  <p>What is happening? I need to retain the list values but <code>unlist()</code> gives me an extra.</p>