The Complete Rust Programming Reference Guide

Taking messages out

Removing the first item in a Vec<T> is not difficult—in fact, Vec<T> ships with a swap_remove() function that does exactly what a heap needs: removing the first element of a Vec<T> by replacing it with the last element! This makes the code significantly shorter and therefore easier to reason about:

pub fn pop(&mut self) -> Option<MessageNotification> {    if self.length > 0 {        let elem = self.heap.swap_remove(0);        self.length = self.heap.len();        let mut i = 1;        while i * 2 < self.length {            let children = (i * 2, i * 2 + 1);            i = if self.has_more_messages(children.0, children.1) {                if self.has_more_messages(children.0, i) {                    self.swap(i, children.0);                    children.0                } else {                    break;                }            } else {                if self.has_more_messages(children.1, i) { ...