Custom Display + Debug Implementation

use std::fmt;

#[derive(Debug)]
struct Money {
    cents: u64,
    currency: &'static str,
}

impl fmt::Display for Money {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        let dollars = self.cents / 100;
        let cents   = self.cents % 100;
        write!(f, "{}{}.{:02}", self.currency, dollars, cents)
    }
}

fn main() {
    let price = Money { cents: 4_99, currency: "$" };
    println!("{price}");      // $4.99    (uses Display)
    println!("{price:?}");    // Money { cents: 499, currency: "$" }   (Debug)
    println!("{price:#?}");   // Same, pretty-printed
}