flux VS RxCpp

flux (https://github.com/tcbrindle/flux) (like ranges::views)

Some people are "Rustifying" their C++ programs also. C++ tooling keeps getting better and libraries like Flux are coming on-line.

Have I got just the thing for you

The code is available on Github of course if you want to check it out, and there's a little bit of documentation covering some of the sequence adaptors and algorithms which are available.

What I've been doing in my projects lately is bundling catch.hpp, then compiling a single catch_main.cpp as a static lib which links to my test exe, and also precompiling catch.hpp when CMake is new enough. You can see an example here.

And, prior to that https://github.com/ReactiveX/RxCpp

Yeah, I know this problem with operators =), original RxCpp implementation also has this problem with implementing all functions into base class and calling dependent functions internally.

Also you can check rxcpp with documentation about reactive approach there. It is functional version of observer/publisher-subscriber patterns with ability to be multithreaded. You can send events from one side, subscribe from another and modify events in meanwhile

I use a very large header-only library RxCpp. Simply adding #include "RxCpp/rx.hpp" to one .cpp file adds >1 second of compilation time. I'd like to use it as a module, but when I try to import "RxCpp/rx.hpp";, I get a bunch of errors.

+1 for Rx, specifically RxCpp. I've used it in concert with Qt with great results.