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-rw-r--r--third_party/rust/itertools/src/adaptors/coalesce.rs235
1 files changed, 235 insertions, 0 deletions
diff --git a/third_party/rust/itertools/src/adaptors/coalesce.rs b/third_party/rust/itertools/src/adaptors/coalesce.rs
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+++ b/third_party/rust/itertools/src/adaptors/coalesce.rs
@@ -0,0 +1,235 @@
+use std::fmt;
+use std::iter::FusedIterator;
+
+use crate::size_hint;
+
+#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
+pub struct CoalesceBy<I, F, T>
+where
+ I: Iterator,
+{
+ iter: I,
+ last: Option<T>,
+ f: F,
+}
+
+impl<I: Clone, F: Clone, T: Clone> Clone for CoalesceBy<I, F, T>
+where
+ I: Iterator,
+{
+ clone_fields!(last, iter, f);
+}
+
+impl<I, F, T> fmt::Debug for CoalesceBy<I, F, T>
+where
+ I: Iterator + fmt::Debug,
+ T: fmt::Debug,
+{
+ debug_fmt_fields!(CoalesceBy, iter);
+}
+
+pub trait CoalescePredicate<Item, T> {
+ fn coalesce_pair(&mut self, t: T, item: Item) -> Result<T, (T, T)>;
+}
+
+impl<I, F, T> Iterator for CoalesceBy<I, F, T>
+where
+ I: Iterator,
+ F: CoalescePredicate<I::Item, T>,
+{
+ type Item = T;
+
+ fn next(&mut self) -> Option<Self::Item> {
+ // this fuses the iterator
+ let last = self.last.take()?;
+
+ let self_last = &mut self.last;
+ let self_f = &mut self.f;
+ Some(
+ self.iter
+ .try_fold(last, |last, next| match self_f.coalesce_pair(last, next) {
+ Ok(joined) => Ok(joined),
+ Err((last_, next_)) => {
+ *self_last = Some(next_);
+ Err(last_)
+ }
+ })
+ .unwrap_or_else(|x| x),
+ )
+ }
+
+ fn size_hint(&self) -> (usize, Option<usize>) {
+ let (low, hi) = size_hint::add_scalar(self.iter.size_hint(), self.last.is_some() as usize);
+ ((low > 0) as usize, hi)
+ }
+
+ fn fold<Acc, FnAcc>(self, acc: Acc, mut fn_acc: FnAcc) -> Acc
+ where
+ FnAcc: FnMut(Acc, Self::Item) -> Acc,
+ {
+ if let Some(last) = self.last {
+ let mut f = self.f;
+ let (last, acc) = self.iter.fold((last, acc), |(last, acc), elt| {
+ match f.coalesce_pair(last, elt) {
+ Ok(joined) => (joined, acc),
+ Err((last_, next_)) => (next_, fn_acc(acc, last_)),
+ }
+ });
+ fn_acc(acc, last)
+ } else {
+ acc
+ }
+ }
+}
+
+impl<I: Iterator, F: CoalescePredicate<I::Item, T>, T> FusedIterator for CoalesceBy<I, F, T> {}
+
+/// An iterator adaptor that may join together adjacent elements.
+///
+/// See [`.coalesce()`](crate::Itertools::coalesce) for more information.
+pub type Coalesce<I, F> = CoalesceBy<I, F, <I as Iterator>::Item>;
+
+impl<F, Item, T> CoalescePredicate<Item, T> for F
+where
+ F: FnMut(T, Item) -> Result<T, (T, T)>,
+{
+ fn coalesce_pair(&mut self, t: T, item: Item) -> Result<T, (T, T)> {
+ self(t, item)
+ }
+}
+
+/// Create a new `Coalesce`.
+pub fn coalesce<I, F>(mut iter: I, f: F) -> Coalesce<I, F>
+where
+ I: Iterator,
+{
+ Coalesce {
+ last: iter.next(),
+ iter,
+ f,
+ }
+}
+
+/// An iterator adaptor that removes repeated duplicates, determining equality using a comparison function.
+///
+/// See [`.dedup_by()`](crate::Itertools::dedup_by) or [`.dedup()`](crate::Itertools::dedup) for more information.
+pub type DedupBy<I, Pred> = CoalesceBy<I, DedupPred2CoalescePred<Pred>, <I as Iterator>::Item>;
+
+#[derive(Clone)]
+pub struct DedupPred2CoalescePred<DP>(DP);
+
+impl<DP> fmt::Debug for DedupPred2CoalescePred<DP> {
+ debug_fmt_fields!(DedupPred2CoalescePred,);
+}
+
+pub trait DedupPredicate<T> {
+ // TODO replace by Fn(&T, &T)->bool once Rust supports it
+ fn dedup_pair(&mut self, a: &T, b: &T) -> bool;
+}
+
+impl<DP, T> CoalescePredicate<T, T> for DedupPred2CoalescePred<DP>
+where
+ DP: DedupPredicate<T>,
+{
+ fn coalesce_pair(&mut self, t: T, item: T) -> Result<T, (T, T)> {
+ if self.0.dedup_pair(&t, &item) {
+ Ok(t)
+ } else {
+ Err((t, item))
+ }
+ }
+}
+
+#[derive(Clone, Debug)]
+pub struct DedupEq;
+
+impl<T: PartialEq> DedupPredicate<T> for DedupEq {
+ fn dedup_pair(&mut self, a: &T, b: &T) -> bool {
+ a == b
+ }
+}
+
+impl<T, F: FnMut(&T, &T) -> bool> DedupPredicate<T> for F {
+ fn dedup_pair(&mut self, a: &T, b: &T) -> bool {
+ self(a, b)
+ }
+}
+
+/// Create a new `DedupBy`.
+pub fn dedup_by<I, Pred>(mut iter: I, dedup_pred: Pred) -> DedupBy<I, Pred>
+where
+ I: Iterator,
+{
+ DedupBy {
+ last: iter.next(),
+ iter,
+ f: DedupPred2CoalescePred(dedup_pred),
+ }
+}
+
+/// An iterator adaptor that removes repeated duplicates.
+///
+/// See [`.dedup()`](crate::Itertools::dedup) for more information.
+pub type Dedup<I> = DedupBy<I, DedupEq>;
+
+/// Create a new `Dedup`.
+pub fn dedup<I>(iter: I) -> Dedup<I>
+where
+ I: Iterator,
+{
+ dedup_by(iter, DedupEq)
+}
+
+/// An iterator adaptor that removes repeated duplicates, while keeping a count of how many
+/// repeated elements were present. This will determine equality using a comparison function.
+///
+/// See [`.dedup_by_with_count()`](crate::Itertools::dedup_by_with_count) or
+/// [`.dedup_with_count()`](crate::Itertools::dedup_with_count) for more information.
+pub type DedupByWithCount<I, Pred> =
+ CoalesceBy<I, DedupPredWithCount2CoalescePred<Pred>, (usize, <I as Iterator>::Item)>;
+
+#[derive(Clone, Debug)]
+pub struct DedupPredWithCount2CoalescePred<DP>(DP);
+
+impl<DP, T> CoalescePredicate<T, (usize, T)> for DedupPredWithCount2CoalescePred<DP>
+where
+ DP: DedupPredicate<T>,
+{
+ fn coalesce_pair(
+ &mut self,
+ (c, t): (usize, T),
+ item: T,
+ ) -> Result<(usize, T), ((usize, T), (usize, T))> {
+ if self.0.dedup_pair(&t, &item) {
+ Ok((c + 1, t))
+ } else {
+ Err(((c, t), (1, item)))
+ }
+ }
+}
+
+/// An iterator adaptor that removes repeated duplicates, while keeping a count of how many
+/// repeated elements were present.
+///
+/// See [`.dedup_with_count()`](crate::Itertools::dedup_with_count) for more information.
+pub type DedupWithCount<I> = DedupByWithCount<I, DedupEq>;
+
+/// Create a new `DedupByWithCount`.
+pub fn dedup_by_with_count<I, Pred>(mut iter: I, dedup_pred: Pred) -> DedupByWithCount<I, Pred>
+where
+ I: Iterator,
+{
+ DedupByWithCount {
+ last: iter.next().map(|v| (1, v)),
+ iter,
+ f: DedupPredWithCount2CoalescePred(dedup_pred),
+ }
+}
+
+/// Create a new `DedupWithCount`.
+pub fn dedup_with_count<I>(iter: I) -> DedupWithCount<I>
+where
+ I: Iterator,
+{
+ dedup_by_with_count(iter, DedupEq)
+}