Huh, I always thought that there is an optimization to always choose the most consty and referency option possible. So if you write `auto` but don't modify the

Huh, I always thought that there is an optimization to always choose the most consty and referency option possible. So if you write `auto` but don't modify the item in the loop, it may choose to use a reference / pointer under the hood, as if you wrote `auto &` or `const auto &`. But it can't strip away the `&`. The reason is that I imagined C++ can substitute anything for auto, so it can make `auto` into a pointer to Foo, but it can't turn `auto &` into `Foo`. (In a first pass, of course due to the as-if rule the compiler can do whatever it wants when you are not looking.) In the example the author reccommends against, `for (const auto x : range)`, I would think it means: - const: don't let me modify x (enforce const-correctness at compile time) - Make a copy or reference, whatever is faster. Particularly, I think/thought: `const` does not tell the compiler to make a copy. The lack of `&` allows the compiler to make a copy. I'm sure this interpretation is not 100% what's in the standard, but a intuition I developed from observation, so probably some of it is wrong.