std::string& ltrim(std::string& str, const std::string& chars = "\t\n\v\f\r ")
{
	str.erase(0, str.find_first_not_of(chars));
	return str;
}
 
std::string& rtrim(std::string& str, const std::string& chars = "\t\n\v\f\r ")
{
	str.erase(str.find_last_not_of(chars) + 1);
	return str;
}
 
std::string& trim(std::string& str, const std::string& chars = "\t\n\v\f\r ")
{
	return ltrim(rtrim(str, chars), chars);
}