title: Starting loop at specific index of a std::string?
body: <p>I wrote the following function:</p>
  <pre><code>std::regex r(&quot;&quot;);
  
  for (std::sregex_iterator i = words_begin; i != words_end; ++i) {}
  </code></pre>
  <p>It starts looking for regex matches from the beginning of the given string (<code>str</code>) But how may I tell it to exclude everything before specific index?</p>
  <p>For example I want it to delete with all of what comes after index number 4 (Not including it).</p>
  <p>Note: I am calling this code from another function so I tried something like <code>str + 4</code> in the string parameter but I got an error that it's not l-value.</p>