If you have a hot loop where it matters, you can put an assert outside the loop which lets llvm remove the bounds checks. Or use unsafe { get_unchecked() } to remove the bounds check entirely.
Exactly, yes. I know it's possible, of course it's possible, its just not trivial like it is in C++.
Most developers I have met don't know how to use a profiler, so not sure any of this discussion matters at all anyway, but I feel like it's important to note when the default in Rust is safe, whereas the default in C++ is fast (and more or less unsafe)
Eh, that argument cuts both ways. Lots of the defaults in C++ are bad. Like, most people don’t know how compiling all your code in a single code unit will improve performance. Or how to do it. In rust it’s a single flag in cargo.toml which is widely talked about. Rust has a much better, faster standard library than C++. Any code which makes heavy use of - for example - sorting in C++ and rust will favour rust because it uses a better algorithm by default.
Rust had the opportunity to iterate on C++’s default choices and improve on them in many cases. I’m not convinced that naive C++ is particularly efficient.
(That said, lots of rust beginners make heavy use of Box and clone() and write inefficient programs that way. It’s hard to actually measure average, beginner code.)
Most developers I have met don't know how to use a profiler, so not sure any of this discussion matters at all anyway, but I feel like it's important to note when the default in Rust is safe, whereas the default in C++ is fast (and more or less unsafe)