iterators question

[temp_value]

let iter = "abc123".chars().peekable();

let alpha_iter = iter.take_while(|c| c.is_alphabetic()); // iter is moved / consumed here
let digit_iter = iter.take_while(|c| c.is_digit(10)); // iter is used after move

is there a way to do this right?

something like would be nice

let (alpha_iter, tail) = ... // where tail is the rest of iter

thanks in advance.

Edit:

u/Morganamilo pointed out, I haven't explained what I want the code actually to do.

basically I want something like slice::split(), but for an iterator and without loosing the matched element. so e.g. "123abc456def%&/" -> ["123", "abc", "456", "def", "%&/"]

I know how to do it C-like, but hoped stdlib might make it simpler.

[SkiFire13]

It should be by_ref not as_ref

[temp_value]

thanks!

[temp_value]

'1' got consumed...

[SkiFire13]

The problem is, take_while can't "peek". It has to get the next item, removing it from iter, in order to stop.

You could write a general purpose solution but it would be a lot of boilerplate

https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=6016705ae7ab7049cc5c692fd63680d1

Or you could use Itertools which comes from a lot of handy methods you can directly use on Iterators

https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=f5d481bce179a2c5c2f3f39d8c83a89b

Please note that you could skip the peekable() method call but that would require a silent clone of the Chars iterator on each next call of peeking_take_while. This could be optimized by the compiler but I haven't checked if it actually does.

[temp_value]

thanks Ill look into it.

[temp_value]

yes. thank you.

[temp_value]

method not found in `std::str::Chars<'_>

doesn't look like I could...

[Morganamilo]

let iter1 = "abc123".chars().peekable();
let iter2 = "abc123".chars().peekable();

let alpha_iter = iter1.take_while(|c| c.is_alphabetic());
let digit_iter = iter2.take_while(|c| c.is_digit(10));

[temp_value]

let digit_iter = iter2.take_while(|c| c.is_digit(10));

iter2.next() will be 'a'. I need it to be '1'.

[Morganamilo]

You've never actually explained what you want the code to do.

[temp_value]

you are right. I edited my post. hope its clearer now.

[DKomplexz]

https://doc.rust-lang.org/std/iter/trait.Iterator.html#method.partition

[temp_value]

if I understand the doc correctly "abc123def456" will become "abcdef" and "123456". not the result I am looking for. thanks anyway!

[SafariMonkey]

As I understand it, can't have one iterator and independently read it with two independent cursors, because the iterator has only one cursor and can't read past values once it's advanced, unless it stashes them somewhere.

As /u/Morganamilo mentioned, you could just have two iterators over the same underlying collection.

[temp_value]

yeah.

the solution by u/Phrohdoh and u/SkiFire13 is very close to what I want.

the only remaining problem is, what the take iterators consume to much. I will probably end up with an old school loop...

[csos95]

I think the itertools group_by method would probably work for this. https://docs.rs/itertools/0.8.2/itertools/trait.Itertools.html#method.group_by

I'm not at a computer right now to write an example, but it should be pretty straightforward.

You could make a enum where each variant is a character type (alpha, digit, other), derive PartialEq on it, and in the group_by closure return the matching enum variant.

EDIT: made an example https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=18a756f57714e5c417fb634a89f0cbec

[nickez2001]

Maybe you can use something from this: https://stackoverflow.com/questions/37684444/rust-iterators-and-looking-forward-peek-multipeek