commit | d434d828df32aeabec2e88130d553616bdde166f | [log] [tgz] |
---|---|---|
author | Chih-Hung Hsieh <chh@google.com> | Fri Aug 28 00:30:44 2020 +0000 |
committer | Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com> | Fri Aug 28 00:30:44 2020 +0000 |
tree | 9b757dc2e66cd46529372fb44c2142c659282eee | |
parent | 51d8b68bbc31f85b9121183225622d7f7bbf2242 [diff] | |
parent | c6d5c2215ce25376e713c2ff6d19be6edcc521fa [diff] |
Fix peeking_take_while/METADATA am: 5e24ce8a75 am: 6eb7bfce97 am: 4419cf83ab am: 3adb18d7a5 am: 2fd07c1fcc am: c6d5c2215c Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/peeking_take_while/+/1414017 Change-Id: I9319bde6b54e77d76ac5627f75c931a76589e81e
peeking_take_while
Provides the peeking_take_while
iterator adaptor method.
The peeking_take_while
method is very similar to take_while
, but behaves differently when used with a borrowed iterator (perhaps returned by Iterator::by_ref
).
peeking_take_while
peeks at the next item in the iterator and runs the predicate on that peeked item. This avoids consuming the first item yielded by the underlying iterator for which the predicate returns false
. On the other hand, take_while
will consume that first item for which the predicate returns false
, and it will be lost.
extern crate peeking_take_while; // Bring the `peeking_take_while` method for peekable iterators into // scope. use peeking_take_while::PeekableExt; // Let's say we have two collections we want to iterate through: `xs` and // `ys`. We want to perform one operation on all the leading contiguous // elements that match some predicate, and a different thing with the rest of // the elements. With the `xs`, we will use the normal `take_while`. With the // `ys`, we will use `peeking_take_while`. let xs: Vec<u8> = (0..100).collect(); let ys = xs.clone(); let mut iter_xs = xs.into_iter(); let mut iter_ys = ys.into_iter().peekable(); { // Let's do one thing with all the items that are less than 10. let xs_less_than_ten = iter_xs.by_ref().take_while(|x| *x < 10); for x in xs_less_than_ten { do_things_with(x); } let ys_less_than_ten = iter_ys.by_ref().peeking_take_while(|y| *y < 10); for y in ys_less_than_ten { do_things_with(y); } } // And now we will do some other thing with the items that are greater than // or equal to 10. // ...except, when using plain old `take_while` we lost 10! assert_eq!(iter_xs.next(), Some(11)); // However, when using `peeking_take_while` we did not! Great! assert_eq!(iter_ys.next(), Some(10));