#![allow(unused_variables)]
#![feature(btree_extract_if)]
fn main() {
    use std::collections::BTreeSet;
    let mut set: BTreeSet<i32> = (0..8).collect();
    let evens: BTreeSet<_> = set.extract_if(.., |v| v % 2 == 0).collect();
    let odds = set;
    assert_eq!(evens.into_iter().collect::< Vec < _ >> (), vec![0, 2, 4, 6]);
    assert_eq!(odds.into_iter().collect::< Vec < _ >> (), vec![1, 3, 5, 7]);
    let mut set: BTreeSet<i32> = (0..8).collect();
    let low: BTreeSet<_> = set.extract_if(0..4, |_v| true).collect();
    let high = set;
    assert_eq!(low.into_iter().collect::< Vec < _ >> (), [0, 1, 2, 3]);
    assert_eq!(high.into_iter().collect::< Vec < _ >> (), [4, 5, 6, 7]);
}