mp-units VS UNITS

It's not the type system you're complaining about, though. It takes a bit of work but you can write types that include units information with no loss of performance.

I recommend using this as reference https://github.com/mpusz/units it probably solves the same or similar problem.

Yep. And there are some libraries to provide strong-type int, depending on what you need: type_safe or even units.

Indeed you cannot. Then again, you couldn't write a library like fmtlib in C in the first place. I mean why do you complain about C++ features which enable you to write libraries you otherwise couldn't? How would you expect to implement equivalent libraries to EVE or mp-units in C alone?

How does it compare with https://github.com/mpusz/units ?

I don't have a book to recommend, but I have a fantastic library: https://github.com/mpusz/units

Good C++ library for that topic is [0]. You can even go further and combine with something like [1] which is super helpful for kalman filters and other stuff where you have heterogeneous units in one vector.

[0] https://github.com/mpusz/units

This seems to be on a progress to standardisation for c++23/26: https://github.com/mpusz/units

C++ Version

You may be right about this. I'm actually mainly concerned about including as just including it can increase binary size substantially, see e.g. https://github.com/nholthaus/units/issues/32

I personally use, and recommend, the units library by Holthaus: https://github.com/nholthaus/units