intersect (pbyte -w res, int res_length,
           pbyte    src, int src_length, 
           pbyte    arg, int arg_length)
{
  byte_exists (byte byte)
  {
    for (int cntr = 0; cntr < arg_length; cntr ++)
    {
      if (byte == arg[cntr]) return 1;
    }
    else
    {
      return 0;
    }
  }

  ulong res_top = 0;

  for (int cntr = 0; cntr < src_length; cntr ++)
  {
    if (byte_exists (src[cntr]))
    {
      ...
    }
  }
}
