How is Display "cleaner" than Debug?

Question

In the Display chapter of Rust By Example, it describes Display as "cleaner" than Debug.

fmt::Debug hardly looks compact and clean ...

fmt::Display may be cleaner than fmt::Debug but ...

How is this? From what I see, you have to do more work and write more code to try and make Display work while Debug works right off the bat! Am I misunderstanding something about what "cleaner code" is, or is this a typo?

Answer 1

Display's output is usually cleaner than Debug's, not the code to implement it. Debug's output is intended to be used for debug purposes, providing a less ambiguous output. Display's output is for user-facing output, so it's highly dependent on the meaning of your structure and that's why it cannot be derived.

For example, consider the following code:

fn main() {
    // Note that \t is the TAB character
    let output = "N\tO\tI\tC\tE";
    println!("Debug: {:?}", output);
    println!("Display: {}", output);
}

It will output:

Debug: "N\tO\tI\tC\tE"
Display: N  O   I   C   E

In this case, Debug will show the characters that the str (text) contains (as its more useful when debugging), while Display will just print them.