1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
use std::iter::Fuse;
use super::size_hint;
#[derive(Clone)]
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[derive(Debug)]
pub struct Intersperse<I>
where I: Iterator
{
element: I::Item,
iter: Fuse<I>,
peek: Option<I::Item>,
}
pub fn intersperse<I>(iter: I, elt: I::Item) -> Intersperse<I>
where I: Iterator
{
let mut iter = iter.fuse();
Intersperse {
peek: iter.next(),
iter,
element: elt,
}
}
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.peek.is_some() {
self.peek.take()
} else {
self.peek = self.iter.next();
if self.peek.is_some() {
Some(self.element.clone())
} else {
None
}
}
}
fn size_hint(&self) -> (usize, Option<usize>) {
let has_peek = self.peek.is_some() as usize;
let sh = self.iter.size_hint();
size_hint::add_scalar(size_hint::add(sh, sh), has_peek)
}
fn fold<B, F>(mut self, init: B, mut f: F) -> B where
Self: Sized, F: FnMut(B, Self::Item) -> B,
{
let mut accum = init;
if let Some(x) = self.peek.take() {
accum = f(accum, x);
}
let element = &self.element;
self.iter.fold(accum,
|accum, x| {
let accum = f(accum, element.clone());
let accum = f(accum, x);
accum
})
}
}