Why PeekingNext does not provide peek method?
#583
Comments
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I think this can be implemented with something like this: fn peek(&mut self) -> bool {
let mut element;
self.peeking_next(|x| {
element = x;
false
});
element
} |
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I see, that's not really clean but it does work. Thanks. |
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I agree that implementing |
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Dec 29, 2021
593: EitherOrBoth: Add or and or_else methods to simplify getting default values r=phimuemue a=carl-anders
## Introducing `or` and `or_else` methods to `EitherOrBoth`
This feature reduces the amount of code required to get specific default values when using EitherOrBoth.
An example of the current way of using `zip_longest` with custom default values:
```rust
let a = (0..=4).into_iter();
let b = (0..=2).into_iter();
let c = a.zip_longest(b).map(|e| match e {
EitherOrBoth::Both(l, r) => (l, r),
EitherOrBoth::Left(l) => (l, 2),
EitherOrBoth::Right(r) => (4, r),
});
// c will now contain an iterator with (0,0), (1,1), (2,2), (3,2), (4,2).
```
An example with the proposed `or` method:
```rust
let a = (0..=4).into_iter();
let b = (0..=2).into_iter();
let c = a.zip_longest(b).map(|e| e.or(4, 2));
// c will now contain an iterator with (0,0), (1,1), (2,2), (3,2), (4,2).
```
I have also included the `or_else` method which does the same but with closures.
## Contribute questions
> Include tests for your new feature, preferably a QuickCheck test
There are no tests for the other `EitherOrBoth` methods, so I was unsure how to place them. However, I have added **DocTest**'s to both methods. These examples allows for easier to understand documentation, and also tests the validity of the methods.
> For new features, please first consider filing a PR to rust-lang/rust
The EitherOrBoth struct does not exist in rust std library.
## Concerns
The naming is slightly inconsistent when compared to rust's `std::Option`, considering the naming from there the added methods should be named `unwrap_or` and `unwrap_or_else`.
However, this would then become inconsistent with the existing method `EitherOrBoth::or_default`. Which is why I went with the chosen names.
I can change the method names if needed, but then we should consider changing `or_default` too.
## P.S.
The `CHANGELOG.md` file has the text `Add EitherOrBoth::or_default (#583)`. This number is wrong, it should be #538.
Co-authored-by: Carl Andersson <carl@carlandersson.net>
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In my understanding,
PeekingNextis a iterator from which we can obtain the reference to the next element. Currently this trait requirespeeking_nextfunction, that consumes the next element when the predicate is satisfied. But what if I want thepeekbehavior, in which the next element is not consumed? I think it is reasonable to provide such trait method too. Is there a reason that there isn't?The text was updated successfully, but these errors were encountered: