use super::Peekable;
#[unstable(feature = "iter_intersperse", reason = "recently added", issue = "79524")]
#[derive(Debug, Clone)]
pub struct Intersperse<I: Iterator>
where
I::Item: Clone,
{
separator: I::Item,
iter: Peekable<I>,
needs_sep: bool,
}
impl<I: Iterator> Intersperse<I>
where
I::Item: Clone,
{
pub(in crate::iter) fn new(iter: I, separator: I::Item) -> Self {
Self { iter: iter.peekable(), separator, needs_sep: false }
}
}
#[unstable(feature = "iter_intersperse", reason = "recently added", issue = "79524")]
impl<I> Iterator for Intersperse<I>
where
I: Iterator,
I::Item: Clone,
{
type Item = I::Item;
#[inline]
fn next(&mut self) -> Option<I::Item> {
if self.needs_sep && self.iter.peek().is_some() {
self.needs_sep = false;
Some(self.separator.clone())
} else {
self.needs_sep = true;
self.iter.next()
}
}
fn fold<B, F>(self, init: B, f: F) -> B
where
Self: Sized,
F: FnMut(B, Self::Item) -> B,
{
let separator = self.separator;
intersperse_fold(self.iter, init, f, move || separator.clone(), self.needs_sep)
}
fn size_hint(&self) -> (usize, Option<usize>) {
intersperse_size_hint(&self.iter, self.needs_sep)
}
}
#[unstable(feature = "iter_intersperse", reason = "recently added", issue = "79524")]
pub struct IntersperseWith<I, G>
where
I: Iterator,
{
separator: G,
iter: Peekable<I>,
needs_sep: bool,
}
#[unstable(feature = "iter_intersperse", reason = "recently added", issue = "79524")]
impl<I, G> crate::fmt::Debug for IntersperseWith<I, G>
where
I: Iterator + crate::fmt::Debug,
I::Item: crate::fmt::Debug,
G: crate::fmt::Debug,
{
fn fmt(&self, f: &mut crate::fmt::Formatter<'_>) -> crate::fmt::Result {
f.debug_struct("IntersperseWith")
.field("separator", &self.separator)
.field("iter", &self.iter)
.field("needs_sep", &self.needs_sep)
.finish()
}
}
#[unstable(feature = "iter_intersperse", reason = "recently added", issue = "79524")]
impl<I, G> crate::clone::Clone for IntersperseWith<I, G>
where
I: Iterator + crate::clone::Clone,
I::Item: crate::clone::Clone,
G: Clone,
{
fn clone(&self) -> Self {
IntersperseWith {
separator: self.separator.clone(),
iter: self.iter.clone(),
needs_sep: self.needs_sep.clone(),
}
}
}
impl<I, G> IntersperseWith<I, G>
where
I: Iterator,
G: FnMut() -> I::Item,
{
pub(in crate::iter) fn new(iter: I, separator: G) -> Self {
Self { iter: iter.peekable(), separator, needs_sep: false }
}
}
#[unstable(feature = "iter_intersperse", reason = "recently added", issue = "79524")]
impl<I, G> Iterator for IntersperseWith<I, G>
where
I: Iterator,
G: FnMut() -> I::Item,
{
type Item = I::Item;
#[inline]
fn next(&mut self) -> Option<I::Item> {
if self.needs_sep && self.iter.peek().is_some() {
self.needs_sep = false;
Some((self.separator)())
} else {
self.needs_sep = true;
self.iter.next()
}
}
fn fold<B, F>(self, init: B, f: F) -> B
where
Self: Sized,
F: FnMut(B, Self::Item) -> B,
{
intersperse_fold(self.iter, init, f, self.separator, self.needs_sep)
}
fn size_hint(&self) -> (usize, Option<usize>) {
intersperse_size_hint(&self.iter, self.needs_sep)
}
}
fn intersperse_size_hint<I>(iter: &I, needs_sep: bool) -> (usize, Option<usize>)
where
I: Iterator,
{
let (lo, hi) = iter.size_hint();
let next_is_elem = !needs_sep;
(
lo.saturating_sub(next_is_elem as usize).saturating_add(lo),
hi.and_then(|hi| hi.saturating_sub(next_is_elem as usize).checked_add(hi)),
)
}
fn intersperse_fold<I, B, F, G>(
mut iter: I,
init: B,
mut f: F,
mut separator: G,
needs_sep: bool,
) -> B
where
I: Iterator,
F: FnMut(B, I::Item) -> B,
G: FnMut() -> I::Item,
{
let mut accum = init;
if !needs_sep {
if let Some(x) = iter.next() {
accum = f(accum, x);
} else {
return accum;
}
}
iter.fold(accum, |mut accum, x| {
accum = f(accum, separator());
accum = f(accum, x);
accum
})
}