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Contents?: true
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Versions: 13
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Contents
use std::iter::FusedIterator;
/// An iterator that produces *n* repetitions of an element.
///
/// See [`repeat_n()`](crate::repeat_n) for more information.
#[must_use = "iterators are lazy and do nothing unless consumed"]
#[derive(Clone, Debug)]
pub struct RepeatN<A> {
pub(crate) elt: Option<A>,
n: usize,
}
/// Create an iterator that produces `n` repetitions of `element`.
pub fn repeat_n<A>(element: A, n: usize) -> RepeatN<A>
where
A: Clone,
{
if n == 0 {
RepeatN { elt: None, n }
} else {
RepeatN {
elt: Some(element),
n,
}
}
}
impl<A> Iterator for RepeatN<A>
where
A: Clone,
{
type Item = A;
fn next(&mut self) -> Option<Self::Item> {
if self.n > 1 {
self.n -= 1;
self.elt.as_ref().cloned()
} else {
self.n = 0;
self.elt.take()
}
}
fn size_hint(&self) -> (usize, Option<usize>) {
(self.n, Some(self.n))
}
fn fold<B, F>(self, mut init: B, mut f: F) -> B
where
F: FnMut(B, Self::Item) -> B,
{
match self {
Self { elt: Some(elt), n } => {
debug_assert!(n > 0);
init = (1..n).map(|_| elt.clone()).fold(init, &mut f);
f(init, elt)
}
_ => init,
}
}
}
impl<A> DoubleEndedIterator for RepeatN<A>
where
A: Clone,
{
#[inline]
fn next_back(&mut self) -> Option<Self::Item> {
self.next()
}
#[inline]
fn rfold<B, F>(self, init: B, f: F) -> B
where
F: FnMut(B, Self::Item) -> B,
{
self.fold(init, f)
}
}
impl<A> ExactSizeIterator for RepeatN<A> where A: Clone {}
impl<A> FusedIterator for RepeatN<A> where A: Clone {}
Version data entries
13 entries across 13 versions & 1 rubygems