commit | 1b3b525d8b6bab81fcba634f56b908989b244e6d | [log] [tgz] |
---|---|---|
author | Treehugger Robot <treehugger-gerrit@google.com> | Thu Jun 16 00:20:44 2022 +0000 |
committer | Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com> | Thu Jun 16 00:20:44 2022 +0000 |
tree | 1a4ac6ef56079e0283fbd6a91e5b44f6029f9274 | |
parent | df708b47f13b1026d0979c2342b7db987e36f5af [diff] | |
parent | 73623b5b7f07d4bea224e4bb9db4b8a4a34e4518 [diff] |
Merge "Update TEST_MAPPING" am: b64d2b1a58 am: e0b6b4b058 am: 7c6cfb021b am: 9c0effdcb0 am: 73623b5b7f Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/peeking_take_while/+/2125849 Change-Id: If33903604ab2824f2f2ef9fe8e426982281acb62 Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>
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.
// 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));