Tracking Issue for CharIndices::offset function

[TrolledWoods]

Feature gate: #![feature(char_indices_offset)]

This is a tracking issue for the function CharIndices::offset. It returns the byte position of the next character, or the length of the underlying string if there are no more characters. This is useful for getting ranges over strings you're iterating over.

Public API

let mut chars = "a楽".char_indices();

assert_eq!(chars.offset(), 0);
assert_eq!(chars.next(), Some((0, 'a')));

assert_eq!(chars.offset(), 1);
assert_eq!(chars.next(), Some((1, '楽')));

assert_eq!(chars.offset(), 4);
assert_eq!(chars.next(), None);

Steps / History

• Implementation: Added CharIndices::offset function #82585
• Final commenting period (FCP)
• Stabilization PR

Unresolved Questions

• Bad API Tracking Issue for CharIndices::offset function #83871 (comment)

[GilRtr]

Is there anything holding this back?

[pmetzger]

I just realized I desperately wanted this today. As it stands it's rather unpleasant assembling a range of characters in a string because you can't easily get the byte offset of the next character to be the end of the range, so then constructing a slice when what you have now is the last character is unpleasant.

[TrolledWoods]

I realized I sort of forgot about this, sorry about that, is there anything I need to do to move this along in stabilization?

[pmetzger]

No idea but I'd really love to see it stabilized.

[Jay-Madden]

Agreed, this would be very useful

[cogsandsquigs]

Yeah, it'd be really nice to have this finally released in the stable builds. Any progress on this?

[pmetzger]

@TrolledWoods Maybe you can ask around on the Rust dev fora about how to progress this?

[jdahlstrom]

As I learned a while back on u.r.l.o, there's also char::len_utf8 that can be used to construct a slice representing (or ending at) the current char.

[m-ou-se]

@rfcbot merge

[rfcbot]

Team member @m-ou-se 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
• @yaahc

Concerns:

• bad API resolved by Tracking Issue for CharIndices::offset function #83871 (comment)
• better-name resolved by Tracking Issue for CharIndices::offset function #83871 (comment)

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.

[Amanieu]

In my experience, additional methods on iterator types tend to be hard/unergonomic to use. In this case it would be better to return the offset as part of a tuple in the iterator's item type.

@rfcbot concern bad API