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+use super::plumbing::*;
+use super::*;
+use std::iter;
+use std::usize;
+
+/// Iterator adaptor for [the `repeat()` function](fn.repeat.html).
+#[derive(Debug, Clone)]
+pub struct Repeat<T: Clone + Send> {
+ element: T,
+}
+
+/// Creates a parallel iterator that endlessly repeats `elt` (by
+/// cloning it). Note that this iterator has "infinite" length, so
+/// typically you would want to use `zip` or `take` or some other
+/// means to shorten it, or consider using
+/// [the `repeatn()` function](fn.repeatn.html) instead.
+///
+/// # Examples
+///
+/// ```
+/// use rayon::prelude::*;
+/// use rayon::iter::repeat;
+/// let x: Vec<(i32, i32)> = repeat(22).zip(0..3).collect();
+/// assert_eq!(x, vec![(22, 0), (22, 1), (22, 2)]);
+/// ```
+pub fn repeat<T: Clone + Send>(elt: T) -> Repeat<T> {
+ Repeat { element: elt }
+}
+
+impl<T> Repeat<T>
+where
+ T: Clone + Send,
+{
+ /// Takes only `n` repeats of the element, similar to the general
+ /// [`take()`](trait.IndexedParallelIterator.html#method.take).
+ ///
+ /// The resulting `RepeatN` is an `IndexedParallelIterator`, allowing
+ /// more functionality than `Repeat` alone.
+ pub fn take(self, n: usize) -> RepeatN<T> {
+ repeatn(self.element, n)
+ }
+
+ /// Iterates tuples, repeating the element with items from another
+ /// iterator, similar to the general
+ /// [`zip()`](trait.IndexedParallelIterator.html#method.zip).
+ pub fn zip<Z>(self, zip_op: Z) -> Zip<RepeatN<T>, Z::Iter>
+ where
+ Z: IntoParallelIterator,
+ Z::Iter: IndexedParallelIterator,
+ {
+ let z = zip_op.into_par_iter();
+ let n = z.len();
+ self.take(n).zip(z)
+ }
+}
+
+impl<T> ParallelIterator for Repeat<T>
+where
+ T: Clone + Send,
+{
+ type Item = T;
+
+ fn drive_unindexed<C>(self, consumer: C) -> C::Result
+ where
+ C: UnindexedConsumer<Self::Item>,
+ {
+ let producer = RepeatProducer {
+ element: self.element,
+ };
+ bridge_unindexed(producer, consumer)
+ }
+}
+
+/// Unindexed producer for `Repeat`.
+struct RepeatProducer<T: Clone + Send> {
+ element: T,
+}
+
+impl<T: Clone + Send> UnindexedProducer for RepeatProducer<T> {
+ type Item = T;
+
+ fn split(self) -> (Self, Option<Self>) {
+ (
+ RepeatProducer {
+ element: self.element.clone(),
+ },
+ Some(RepeatProducer {
+ element: self.element,
+ }),
+ )
+ }
+
+ fn fold_with<F>(self, folder: F) -> F
+ where
+ F: Folder<T>,
+ {
+ folder.consume_iter(iter::repeat(self.element))
+ }
+}
+
+/// Iterator adaptor for [the `repeatn()` function](fn.repeatn.html).
+#[derive(Debug, Clone)]
+pub struct RepeatN<T: Clone + Send> {
+ element: T,
+ count: usize,
+}
+
+/// Creates a parallel iterator that produces `n` repeats of `elt`
+/// (by cloning it).
+///
+/// # Examples
+///
+/// ```
+/// use rayon::prelude::*;
+/// use rayon::iter::repeatn;
+/// let x: Vec<(i32, i32)> = repeatn(22, 3).zip(0..3).collect();
+/// assert_eq!(x, vec![(22, 0), (22, 1), (22, 2)]);
+/// ```
+pub fn repeatn<T: Clone + Send>(elt: T, n: usize) -> RepeatN<T> {
+ RepeatN {
+ element: elt,
+ count: n,
+ }
+}
+
+impl<T> ParallelIterator for RepeatN<T>
+where
+ T: Clone + Send,
+{
+ type Item = T;
+
+ fn drive_unindexed<C>(self, consumer: C) -> C::Result
+ where
+ C: UnindexedConsumer<Self::Item>,
+ {
+ bridge(self, consumer)
+ }
+
+ fn opt_len(&self) -> Option<usize> {
+ Some(self.count)
+ }
+}
+
+impl<T> IndexedParallelIterator for RepeatN<T>
+where
+ T: Clone + Send,
+{
+ fn drive<C>(self, consumer: C) -> C::Result
+ where
+ C: Consumer<Self::Item>,
+ {
+ bridge(self, consumer)
+ }
+
+ fn with_producer<CB>(self, callback: CB) -> CB::Output
+ where
+ CB: ProducerCallback<Self::Item>,
+ {
+ callback.callback(RepeatNProducer {
+ element: self.element,
+ count: self.count,
+ })
+ }
+
+ fn len(&self) -> usize {
+ self.count
+ }
+}
+
+/// Producer for `RepeatN`.
+struct RepeatNProducer<T: Clone + Send> {
+ element: T,
+ count: usize,
+}
+
+impl<T: Clone + Send> Producer for RepeatNProducer<T> {
+ type Item = T;
+ type IntoIter = Iter<T>;
+
+ fn into_iter(self) -> Self::IntoIter {
+ Iter {
+ element: self.element,
+ count: self.count,
+ }
+ }
+
+ fn split_at(self, index: usize) -> (Self, Self) {
+ (
+ RepeatNProducer {
+ element: self.element.clone(),
+ count: index,
+ },
+ RepeatNProducer {
+ element: self.element,
+ count: self.count - index,
+ },
+ )
+ }
+}
+
+/// Iterator for `RepeatN`.
+///
+/// This is conceptually like `std::iter::Take<std::iter::Repeat<T>>`, but
+/// we need `DoubleEndedIterator` and unconditional `ExactSizeIterator`.
+struct Iter<T: Clone> {
+ element: T,
+ count: usize,
+}
+
+impl<T: Clone> Iterator for Iter<T> {
+ type Item = T;
+
+ #[inline]
+ fn next(&mut self) -> Option<T> {
+ if self.count > 0 {
+ self.count -= 1;
+ Some(self.element.clone())
+ } else {
+ None
+ }
+ }
+
+ #[inline]
+ fn size_hint(&self) -> (usize, Option<usize>) {
+ (self.count, Some(self.count))
+ }
+}
+
+impl<T: Clone> DoubleEndedIterator for Iter<T> {
+ #[inline]
+ fn next_back(&mut self) -> Option<T> {
+ self.next()
+ }
+}
+
+impl<T: Clone> ExactSizeIterator for Iter<T> {
+ #[inline]
+ fn len(&self) -> usize {
+ self.count
+ }
+}