title: Asymmetry of string::find_first_of and string::find_last_of
body: <p>With the member function string::find_first_of in the C++ standard library you can search in the empty substring:</p>
  
  <pre><code> s.find_first_of(c, s.size())
  </code></pre>
  
  <p>or</p>
  
  <pre><code>s.find_first_of(c, string::npos)
  </code></pre>
  
  <p>But you cannot search in the empty substring with <code>string::find_last_of</code>; the next call will search in a substring containing (only) the first character:</p>
  
  <pre><code> s.find_last_of(c, 0)
  </code></pre>
  
  <p>I think it is an imperfection of the C++ standard library, isn't it?</p>