Why is `while` performance considered slower than` for` when repeating an array?

Question

The second edition of the rust programming language describes the following about loops for iterating over an array:

fn main() {
    let a = [10, 20, 30, 40, 50];
    let mut index = 0;

    while index < 5 {
        println!("the value is: {}", a[index]);

        index = index + 1;
    }
}

[...] It is also slow because the compiler adds runtime code to conditionally check each element at each iteration through a loop.

As a more efficient alternative, you can use a for loop and execute code for each item in the collection.

fn main() {
    let a = [10, 20, 30, 40, 50];

    for element in a.iter() {
        println!("the value is: {}", element);
    }
}

In C ++, I would expect the compiler / optimizer to create something with equivalent runtime performance.

Why is this not so in Rust?

Answer 1

In C ++, I would expect the compiler / optimizer to create something with equivalent runtime performance.

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