Add std::str::Chars remaining() function: #12395

[mneumann]

No description provided.

[mneumann]

#12395

[alexcrichton]

I'm a little worried that this doesn't update any of

• rev_chars
• char_indices
• char_indices_rev
• split
• splitn
• words
• ...

The string class has a fair number of iterators. Is there a reason that the chars one should be the only one blessed with this function?

[mneumann]

Will hack that tomorrow, too late here atm :)

[alexcrichton]

I caution you before too much work is put in to this. I pointed out those iterators as an example of where this function may not fit into the library. I would find it a little annoying to have to define remaining for all iterators on strings if we ever add new ones.

I think iterators are really good at doing just that, iterating. Conflating other state with specific iterators reduces the utility of other ones, so we'll want to approach this carefully.

[mneumann]

The thing with strings is that it is pretty hard to safely iterate over them on your own as you need to use char_range_at(). Also by using iterators, I assume that the range checks could be optimized away one day (iterators could be implemented unsafe underneath). remaining also allows us to alternate different iterators:

s.chars(|c| if c == ' ' { break }).remaining().split(',', |tok| {println!("{}", tok)});

[alexcrichton]

Sadly I don't think that iterator will quite work how you expect, because calling chars doesn't actually exhaust the iterator. The return value of remaining() will be the entire string for the code you provided.

[mneumann]

Ooops, of course not. Though this should work:

let mut iter = s.chars();
for c in iter { if c == ' ' { break } }
iter.remaining().split(',', |tok| {println!("{}", tok)});

Or if we'd have each() again as we had some time ago, this would be something like this:

s.chars().each(|c| { c != ' ' }).remaining().split(',', |tok| {println!("{}", tok)});

[alexcrichton]

Closing due to a lack of activity. This may want to get fleshed out and agreed upon first before opening another PR.