#![allow(unused_variables)]
#![feature(btree_set_entry)]
fn main() {
    use std::collections::btree_set::BTreeSet;
    let mut set = BTreeSet::new();
    set.extend(["a", "b", "c"]);
    assert_eq!(set.len(), 3);
    let entry = set.entry("a");
    let _raw_o = entry.insert();
    assert_eq!(set.len(), 3);
    set.entry("d").insert();
    set.entry("b").or_insert();
    set.entry("e").or_insert();
    println!("Our BTreeSet: {:?}", set);
    assert!(set.iter().eq(& ["a", "b", "c", "d", "e"]));
}