> variant isn't, yet. We'll eventually get some kind of structural pattern matching that will make variant or it's successor more idiomatic.
Thats the fantastic thing about c++, you can already write an easy to use match, but they just chose not to include that in the stdlib but rather want you write that yourself.
Also optional and expected are ergonomic nightmares since there is no "try!" macro like rust has. In general it lacks the infrastructure that is needed to make these types nice to use. It also clashes with other concepts like RAII where you kinda have to use exceptions when it comes to ctors that may fail.
It would be pretty ugly to make this more introspective in C++.
For example, if you had to match patterns to distinguish between these three possibilities when looking at a tree: (val), (val (tree left) (tree right)), (val (tree subtree)). Here, the possibilities are not really separate types, but rather different ways of constructing a type. This sort of pattern shows up in general purpose programming (even meat and potato imperative programming) pretty often.
The try! macro was deprecated in 2019 so, almost six years ago. And even before formal deprecation the word try is now a keyword and so you'd need to use r#try! to say you want the obsolete macro not the keyword.
Thats the fantastic thing about c++, you can already write an easy to use match, but they just chose not to include that in the stdlib but rather want you write that yourself.
Example:
Also optional and expected are ergonomic nightmares since there is no "try!" macro like rust has. In general it lacks the infrastructure that is needed to make these types nice to use. It also clashes with other concepts like RAII where you kinda have to use exceptions when it comes to ctors that may fail.