std::string trim( const std::string & str ){
  std::string::size_type startPos = str.find_first_not_of( " " );
  if( startPos != std::string::npos ){
    std::string::size_type endPos = str.find_last_of( " " );
    return ( endPos == std::string::npos ) ? str.substr( startPos ) : str.substr( startPos, endPos - startPos );
  }
  return str;
}