Tracking Issue for `unsigned_is_multiple_of`

[folkertdev]

Feature gate: #![feature(unsigned_is_multiple_of)]
ACP: rust-lang/libs-team#404

This is a tracking issue for the .is_multiple_of method on unsigned integers.

Returns true if self is an integer multiple of rhs, and false otherwise.

This function is equivalent to self % rhs == 0, except that it will not panic for rhs == 0. Instead, 0.is_multiple_of(0) == true, and for any non-zero n, n.is_multiple_of(0) == false.

If you have a real usecase for this function on signed integer types, let us know! That was not included for simplicity, but if a usecase comes up, adding it will be considered.

Public API

A version of this for all the unsigned types

fn is_multiple_of(lhs: u64, rhs: u64) -> bool {
    match rhs {
        // prevent division by zero
        0 => lhs == 0,
        _ => lhs % rhs == 0,
    }
}

Steps / History

• Implementation: add is_multiple_of for unsigned integer types #128103
• Final comment period (FCP)¹
• Stabilization PR stabilize unsigned_is_multiple_of #137383

Unresolved Questions

• None yet.

Footnotes

1. https://std-dev-guide.rust-lang.org/feature-lifecycle/stabilization.html ↩

[diondokter]

I'd love to have this stable at some point. It's not a must have, but it makes code much nicer to read.

In my case right now, I need to check if the hardware busses have dividers that are a multiple of the main bus. You judge what's better to read and conveys more meaning:

let apb_dividers = [config.apb1_divider, config.apb2_divider, config.apb3_divider, config.apb4_divider];
for apb_divider in apb_dividers {
    assert!(
        apb_divider.div_value() % config.core_clock_prescaler.div_value()
            == 0
    );
}

Or

let apb_dividers = [config.apb1_divider, config.apb2_divider, config.apb3_divider, config.apb4_divider];
for apb_divider in apb_dividers {
    assert!(
        apb_divider.div_value()
            .is_multiple_of(config.core_clock_prescaler.div_value())
    );
}

[joshtriplett]

This has been implemented for a while, it's simple and straightforward, it's useful, people want it, and there are no known issues with it.

Shall we stabilize it?

@rfcbot merge

[rfcbot]

Team member @joshtriplett has proposed to merge this. The next step is review by the rest of the tagged team members:

• @Amanieu
• @BurntSushi
• @dtolnay
• @joshtriplett
• @m-ou-se

No concerns currently listed.

Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up!

See this document for info about what commands tagged team members can give me.

[rfcbot]

🔔 This is now entering its final comment period, as per the review above. 🔔