81 lines
1.9 KiB
Rust
81 lines
1.9 KiB
Rust
/// Utilities.
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use std::cmp::Ordering;
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use std::ops::Range;
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/// Additional methods for slices.
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pub trait SliceExt<T> {
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/// Split a slice into consecutive groups with the same key.
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///
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/// Returns an iterator of pairs of a key and the group with that key.
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fn group_by_key<K, F>(&self, f: F) -> GroupByKey<'_, T, F>
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where
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F: FnMut(&T) -> K,
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K: PartialEq;
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}
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impl<T> SliceExt<T> for [T] {
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fn group_by_key<K, F>(&self, f: F) -> GroupByKey<'_, T, F>
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where
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F: FnMut(&T) -> K,
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K: PartialEq,
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{
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GroupByKey { slice: self, f }
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}
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}
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/// This struct is produced by [`SliceExt::group_by_key`].
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pub struct GroupByKey<'a, T, F> {
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slice: &'a [T],
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f: F,
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}
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impl<'a, T, K, F> Iterator for GroupByKey<'a, T, F>
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where
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F: FnMut(&T) -> K,
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K: PartialEq,
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{
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type Item = (K, &'a [T]);
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fn next(&mut self) -> Option<Self::Item> {
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let first = self.slice.first()?;
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let key = (self.f)(first);
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let mut i = 1;
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while self.slice.get(i).map_or(false, |t| (self.f)(t) == key) {
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i += 1;
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}
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let (head, tail) = self.slice.split_at(i);
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self.slice = tail;
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Some((key, head))
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}
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}
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/// Additional methods for [`Range<usize>`].
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pub trait RangeExt {
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/// Locate a position relative to a range.
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///
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/// This can be used for binary searching the range that contains the
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/// position as follows:
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/// ```
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/// # use typst::util::RangeExt;
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/// assert_eq!(
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/// [1..2, 2..7, 7..10].binary_search_by(|r| r.locate(5)),
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/// Ok(1),
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/// );
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/// ```
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fn locate(&self, pos: usize) -> Ordering;
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}
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impl RangeExt for Range<usize> {
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fn locate(&self, pos: usize) -> Ordering {
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if pos < self.start {
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Ordering::Greater
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} else if pos < self.end {
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Ordering::Equal
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} else {
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Ordering::Less
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}
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}
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}
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