Rust BTreeSet::Range::size_hint testing

pinkinvisibleunicorn.rs

// Rust BTreeSet::Range::size_hint testing

use std::collections::btree_set::*;

fn main() {
    let mut treeset = BTreeSet::<u32>::new();
    
    for i in 0..78 {
        if i % 3 != 1 {
            treeset.insert(i);
        }
    }
    
    for x in treeset.iter() {
        print!("{} ", x);
    }
    
    print!("\n");
    
    for x in treeset.range(15..35) {
        print!("{} ", x)
    }
    print!("\n");
    
    let sh = treeset.range(15..35).size_hint();
    
    print!("Range hint = {} {}", sh.0,
        match sh.1 {
            None => -1,
            Some(x) => x as i64
        }
    );
}

// 0 2 3 5 6 8 9 11 12 14 15 17 18 20 21 23 24 26 27 29 30 32 33 35 36 38 39 41 42 44 45 47 48 50 51 53 54 56 57 59 60 62 63 65 66 68 69 71 72 74 75 77 
// 15 17 18 20 21 23 24 26 27 29 30 32 33 
// Range hint = 0 -1

// I expected Range hint to tell me something like at least 0..21
// but seeing the code of btreeset::range + the result of this experiment makes me sad