std::optional


### std::optional usages
|Title|
|:-:|
|[std::nullopt](https://texonom.com/stdnullopt-69fe4b03056e49f4be1fedecabd7fd22)|
|[std::optional<T>::or_else](https://texonom.com/stdoptionaltorelse-54f52e5b6bf442829dd57b502f9edcd3)|
|[std::optional<T>::and_then](https://texonom.com/stdoptionaltandthen-5daba497937643529febff55f1961313)|
|[std::optional<T>::transform](https://texonom.com/stdoptionalttransform-d19b0e416d5e4323a944321cf6d3fe2c)|




> [씹어먹는 C++ - <17 - 5. C++ 17 의 std::optional, variant, tuple 살펴보기>](https://modoocode.com/309)





