BTreeMap::split_off should mention that the key don't need to be exact

[ultimaweapon]

Location (URL)

https://doc.rust-lang.org/std/collections/struct.BTreeMap.html#method.split_off

Summary

The following code is working (as expected?):

use std::collections::BTreeMap;

fn main() {
    let mut a = BTreeMap::new();
    
    a.insert(1, "a");
    a.insert(2, "b");
    a.insert(3, "c");
    a.insert(17, "d");
    a.insert(41, "e");
    
    let b = a.split_off(&4);
    
    assert_eq!(a.len(), 3);
    assert_eq!(b.len(), 2);
}

Notice the split_off call with the key that does not exists in the tree.