Bounds checking is different from the conditional checks in something like a loop. It's the logic that prevents you from accessing memory that isn't yours. If y

Bounds checking is different from the conditional checks in something like a loop. It's the logic that prevents you from accessing memory that isn't yours. If you have an array arr of length 5 in Java, if you do arr[10] you get an IndexOutOfBoundsException because you're not allowed to do that. If you did the same thing in C, you might get some data which is unrelated to your array, or perhaps a segfault. So when you you loop over an array, your loop conditional makes sure that your index hasn't indexed out of bounds, in addition to the bounds checking that is performed when actually indexing the array. So you in a sense pay a double price for the same assurance. (This is modulo compiler optimizations.) Rust has to guarantee memory safety (I guess Java makes the same promise). This means that you have to have bounds checking for array indexing, lest you index out of bounds of some array and get killed by the operating system, if that memory happens to be outside of your process' "turf". You can't eliminate that in general (or; it's hecka hard), but you can probably encapsulate things like iterating over data structures like arrays, vet the code, and say that "this thing loops from 0 to the length of the array minus 1... I swear on my mother's future grave that it is safe to turn off bounds checking for array indexing here." (The way they do it in Rust may be more rigorous than this, for all I know!)