title: Flatten list of negative numbers
body: <p>I am trying to flatten the following type of Tcl lists:</p>
  
  <pre><code>-1587.500000 {} 1587.500000 
  </code></pre>
  
  <p>or</p>
  
  <pre><code>15.78 18.56 {} {} {} {} 15.6
  </code></pre>
  
  <p>So I try:</p>
  
  <pre><code> [struct::list flatten -full $lineToFlatten]
  </code></pre>
  
  <p>But when <code>lineToFlatten</code> starts with the negative number the following type of error message is issued (for example):</p>
  
  <pre><code>  Unknown option "-1587.500000 {} 1587.500000", should be either -full, or --
  </code></pre>
  
  <p>How to resolve this?</p>