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
use crate::common::*;
#[derive(Debug)]
pub struct AndThen<I, F> {
pub(super) iter: Option<I>,
pub(super) f: F,
}
impl<I, F, T, U, E> Iterator for AndThen<I, F>
where
I: Iterator<Item = Result<T, E>>,
F: FnMut(T) -> Result<U, E>,
{
type Item = Result<U, E>;
fn next(&mut self) -> Option<Self::Item> {
let mut iter = match self.iter.take() {
Some(iter) => iter,
None => return None,
};
let input_item = match iter.next() {
Some(Ok(item)) => item,
Some(Err(err)) => {
return Some(Err(err));
}
None => return None,
};
match (self.f)(input_item) {
Ok(output_item) => {
self.iter = Some(iter);
Some(Ok(output_item))
}
Err(err) => Some(Err(err)),
}
}
}