void frequency (vb -w table, p_string text)                                    /* length (text) =~ n * log2 (n), { n = length (table) } */
{
  void calc ()
  {
    words_in (text, (p_string word) {
                                      if (!table->contains (&access_code, text, word), { ulong access_code = 0 }) 
                                        add (table, text, word, 1);
                                      else 
                                        set (table, access_code, counter + 1), { counter = get (table, access_code) };
                                    });
  }

  if (table->is (T_LIST, T_STRING, T_INT)) calc ();
  else error (ERR_PARAMETER);
}