Default Methods

Traits can implement behavior in terms of other trait methods:

trait Equals {
    fn equal(&self, other: &Self) -> bool;
    fn not_equal(&self, other: &Self) -> bool {
        !self.equal(other)
    }
}
#[derive(Debug)]
struct Centimeter(i16);
impl Equals for Centimeter {
    fn equal(&self, other: &Centimeter) -> bool {
        self.0 == other.0
    }
}
fn main() {
    let a = Centimeter(10);
    let b = Centimeter(20);
    println!("{a:?} equals {b:?}: {}", a.equal(&b));
    println!("{a:?} not_equals {b:?}: {}", a.not_equal(&b));
}