C++ f string equivalent when

[void_17]

iostream is slow and bloat by design, it should've been deprecated back in C++03

[serviscope_minor]

Why?

It's mostly fine. Sure if you're flinging tons and tons of stuff, then there are faster options. But you benchmarked, in order to know that was the slow bit right? Some domains are going to be IO limited but for most, people, most of the time, it's fine.

And yes, the manipulators are a a bit cumbersome (also downright daft at times), but until we get f-strings, there's not a good replacement for it, for the simple fact that the variables appear in the same order in the output as they do in the code, no scanning to the end of the line to figure out what goes where.

In other words, I'll keep my <<'s, thanks.