Show how to pass function as argument in Rust.

fn-as-argument.rs

struct Point {
    x: f64,
    y: f64,
}

fn custom(p1: &Point, p2: &Point) -> f64 {
    let dx = p2.x - p1.x;
    let dy = p2.y - p1.y;
    let d = dx * dx + dy * dy;
    return d.sqrt();
}

fn distance(f: fn(&Point, &Point) -> f64) -> f64 {
    let p1 = Point { x: 1.0, y: 1.0 };
    let p2 = Point { x: 1.0, y: 4.0 };

    let d = f(&p1, &p2);

    return d;
}

fn main() {
    let d = distance(custom);
    dbg!(d);
}