Use std::format instead of string concatenation

[mikomikotaishi]

Seeing as the project builds with C++20 which <format> was introduced in, is there any plan to use std::format instead of traditional string concatenation for more versatility?

[ken-matsui]

Are you talking about the Cabin codebase itself? I’m currently using fmtlib, but there might be some code that uses string concat. You’re welcome to make a PR to replace such code with fmtlib.

[mikomikotaishi]

Yeah, the codebase itself has some usage of string concatenations, I don't know how much faster string formatting is especially considering the additional boilerplate in specialising std::formatter compared to operator<<. <format> itself is based off of fmtlib, so I imagine there wouldn't be any problems using it if you use fmtlib already, in fact it would probably be one less dependency to manage (unless fmtlib offers more features not part of <format> that you use).

[ken-matsui]

I’m using features that fmtlib has but <format> doesn’t, such as std formats. A lot seems to be coming in C++26, so perhaps then.

I’m not sure about the performance because it depends on the code. Which part of the code are you referring to?

[mikomikotaishi]

I think it was just a part of New.cc that used string concatenation, which I changed in my PR. If I find any more I'll change it accordingly.