commit | 97eb77360236747f598b7bf8e2e948ed47512899 | [log] [tgz] |
---|---|---|
author | Linux Build Service Account <lnxbuild@localhost> | Wed Jan 26 00:34:49 2022 -0800 |
committer | Linux Build Service Account <lnxbuild@localhost> | Wed Jan 26 00:34:49 2022 -0800 |
tree | d547f05777c5f26dc33a3ecb9ffdfcb7c15e162e | |
parent | 025d6094bafbdd84cf67186f4a7bb99f85574baf [diff] | |
parent | a0a52cf92b664b2a578bb0d9786d30f38d0afe00 [diff] |
Merge a0a52cf92b664b2a578bb0d9786d30f38d0afe00 on remote branch Change-Id: If3f289d6191bb781a488b9c71cdcfa37800216b0
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));