>Concepts are usable in the sense they compile. Claiming they are usable in terms of being ergonomic and that people are willing to use them outside the stdlib

>Concepts are usable in the sense they compile. Claiming they are usable in terms of being ergonomic and that people are willing to use them outside the stdlib is a stretch. You think it seems reasonable until you encounter Rust traits and then you wonder wtf is C++ doing. Concepts work great. The primary purpose of them is to allow things to compile or not and to deliver readable error messages when a constraint is violated. I use them from time to time at work. I don't know about Rust traits but I do know that C++ has many useful paradigms and idioms to handle a variety of sticky situations. >As for modules, it’s now 5 years since standardization. How much more time does a basic feature like that take to mature? It's not as basic as you imagine, evidently. If this was any other language, the one true language authority would start building an implementation with a spec that is constantly in flux, and it could take just as long to complete. Alternatively, they'd break compatibility and shrug off the hundreds of man-years of work they generated downstream. >Btw, the community provided feedback to the standards committee that the spec was useless for anyone building build systems tooling around it and the committee chose to ignore that warning and this is the result. I think this means the committee sees it as someone else's job to develop the implementation details for modules. They also don't specify things such as, how shared libraries should be built or loaded, or the format of binary code. >The committee was actually given a lot of benefit of the doubt after c++11 because they promised to change. They’ve squandered it. They did change. We are getting regular updates and corrections now. I think the committee is more open to proposals than ever, perhaps too open. I can hardly keep up with all the cool stuff they add every couple of years.