bound function not correct about itertools

[kindlychung]

!self.phase && a > b || (self.phase && a < b) seems correct to me.

[bluss]

It has a quickcheck test here https://github.com/bluss/rust-itertools/blob/master/tests/quick.rs#L306

Can you form a testcase that fails?

[kindlychung]

I don't know quickcheck well enough at the moment, but check this out:

extern crate itertools;

use itertools::InterleaveShortest;

fn main() {
    let a = vec![1u32, 2u32, 3u32]; 
    let b = vec![1u32, 2u32, 3u32, 4u32, 5u32, 6u32]; 
    let mut i = InterleaveShortest::new(a.into_iter(), b.into_iter());
    let x = i.next(); 
    println!("{:?}", i.size_hint());
}

This prints (4, Some(5)), which in my opinion is not really accurate, I would expect (5, Some(5)).

[kindlychung]

This produces (5, Some(5)):

        let bound = |a: usize, b: usize| -> Option<usize> {
            use std::cmp::min;
            2usize.checked_mul(min(a, b))
//                .and_then(|lhs| lhs.checked_add(if !self.phase && a > b { 1 } else { 0 }))
                .and_then(|lhs| lhs.checked_add(if  !self.phase && a > b || (self.phase && a < b)  { 1 } else { 0 }))
        };

[bluss]

nice, thanks a lot!