Comparison of num::rational::Ratio is incorrect with overflow

[rust-highfive]

Issue by huonw
Monday Aug 12, 2013 at 09:23 GMT

For earlier discussion, see rust-lang/rust#8466

This issue was labelled with: A-libs in the Rust repository

---

extern crate num;
use num::rational::Ratio;

fn main() {
    let big = Ratio::new(128u8, 1);
    let small = big.recip();
    assert!(big > small);
}

fails the assertion. (It's comparing 128 with 1/128.)

This, or something similar, happens for any type that can overflow (I guess one could argue that fixed size types are "unsupported" for rational numbers, and so this overflow leads to unspecified behaviour).