Ord

trait Ord<T: Lt + Le + Gt + Ge + Eq>

The ordering bundle: Lt, Le, Gt and Ge, with Eq.

Ord has no methods of its own. A bound T: Ord allows <, <=, >, >=, == and != on T, and range bounds (a..b) must be Ord. Eq is a superclass, so a type that is Ord is Eq too: an impl Ord or #[derive(Ord)] needs an Eq instance (#[derive(Eq, Ord)]). int, float, byte and string are ordered (a string by its UTF-8 bytes, so "B" < "a" and a prefix sorts first); bool is not. A string is not a range bound. #[derive(Ord)] orders an enum or class by its fields in declaration order, and a scalar-backed enum (#[repr(int)], #[repr(string)], ..) by its backing value.

A tuple whose elements are all Ord is Ord too, ordered lexicographically: the first element that differs decides ((1, "b") < (2, "a")).

Examples#

use tests::assert;
fn smaller<T: Ord>(T a, T b) -> T {
    if a < b {
        return a;
    }
    return b;
}

fn main() {
    assert!(smaller(3, 2) == 2);
    assert!(smaller(1.5, 2.5) == 1.5);
    assert!(smaller("pear", "fig") == "fig");
    assert!(smaller((1, "b"), (1, "a")) == (1, "a"));
}

See also#

• Lt
• Le
• Gt
• Ge
• Eq
• int
• float
• byte
• string
• bool