n class="hljs-keyword">else</span>:
        <span class="hljs-keyword">raise</span> <span class="hljs-type">ValueError</span>.newException &amp;<span class="hljs-string">&quot;invalid character: '{c}'&quot;</span>
  
  <span class="hljs-keyword">func</span> `$`(n: <span class="hljs-type">Number</span>): <span class="hljs-built_in">string</span> =
    <span class="hljs-keyword">var</span> left: <span class="hljs-built_in">seq</span>[<span class="hljs-built_in">bool</span>]
    <span class="hljs-keyword">for<