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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-06-19 09:26:03 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-06-19 09:26:03 +0000 |
commit | 9918693037dce8aa4bb6f08741b6812923486c18 (patch) | |
tree | 21d2b40bec7e6a7ea664acee056eb3d08e15a1cf /vendor/itertools-0.11.0/src/with_position.rs | |
parent | Releasing progress-linux version 1.75.0+dfsg1-5~progress7.99u1. (diff) | |
download | rustc-9918693037dce8aa4bb6f08741b6812923486c18.tar.xz rustc-9918693037dce8aa4bb6f08741b6812923486c18.zip |
Merging upstream version 1.76.0+dfsg1.
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'vendor/itertools-0.11.0/src/with_position.rs')
-rw-r--r-- | vendor/itertools-0.11.0/src/with_position.rs | 88 |
1 files changed, 88 insertions, 0 deletions
diff --git a/vendor/itertools-0.11.0/src/with_position.rs b/vendor/itertools-0.11.0/src/with_position.rs new file mode 100644 index 000000000..dda9b25dc --- /dev/null +++ b/vendor/itertools-0.11.0/src/with_position.rs @@ -0,0 +1,88 @@ +use std::iter::{Fuse,Peekable, FusedIterator}; + +/// An iterator adaptor that wraps each element in an [`Position`]. +/// +/// Iterator element type is `(Position, I::Item)`. +/// +/// See [`.with_position()`](crate::Itertools::with_position) for more information. +#[must_use = "iterator adaptors are lazy and do nothing unless consumed"] +pub struct WithPosition<I> + where I: Iterator, +{ + handled_first: bool, + peekable: Peekable<Fuse<I>>, +} + +impl<I> Clone for WithPosition<I> + where I: Clone + Iterator, + I::Item: Clone, +{ + clone_fields!(handled_first, peekable); +} + +/// Create a new `WithPosition` iterator. +pub fn with_position<I>(iter: I) -> WithPosition<I> + where I: Iterator, +{ + WithPosition { + handled_first: false, + peekable: iter.fuse().peekable(), + } +} + +/// The first component of the value yielded by `WithPosition`. +/// Indicates the position of this element in the iterator results. +/// +/// See [`.with_position()`](crate::Itertools::with_position) for more information. +#[derive(Copy, Clone, Debug, PartialEq)] +pub enum Position { + /// This is the first element. + First, + /// This is neither the first nor the last element. + Middle, + /// This is the last element. + Last, + /// This is the only element. + Only, +} + +impl<I: Iterator> Iterator for WithPosition<I> { + type Item = (Position, I::Item); + + fn next(&mut self) -> Option<Self::Item> { + match self.peekable.next() { + Some(item) => { + if !self.handled_first { + // Haven't seen the first item yet, and there is one to give. + self.handled_first = true; + // Peek to see if this is also the last item, + // in which case tag it as `Only`. + match self.peekable.peek() { + Some(_) => Some((Position::First, item)), + None => Some((Position::Only, item)), + } + } else { + // Have seen the first item, and there's something left. + // Peek to see if this is the last item. + match self.peekable.peek() { + Some(_) => Some((Position::Middle, item)), + None => Some((Position::Last, item)), + } + } + } + // Iterator is finished. + None => None, + } + } + + fn size_hint(&self) -> (usize, Option<usize>) { + self.peekable.size_hint() + } +} + +impl<I> ExactSizeIterator for WithPosition<I> + where I: ExactSizeIterator, +{ } + +impl<I: Iterator> FusedIterator for WithPosition<I> +{} |