iterator_ext/
try_flat_map.rs

1use crate::common::*;
2
3#[derive(Debug)]
4pub struct TryFlatMap<I, F, J> {
5    pub(super) iter: Option<I>,
6    pub(super) sub_iter: Option<J>,
7    pub(super) f: F,
8}
9
10impl<I, F, J, T, U, V, E> Iterator for TryFlatMap<I, F, J>
11where
12    I: Iterator<Item = Result<T, E>>,
13    J: Iterator<Item = V>,
14    F: FnMut(T) -> Result<U, E>,
15    U: IntoIterator<Item = V, IntoIter = J>,
16{
17    type Item = Result<V, E>;
18
19    fn next(&mut self) -> Option<Self::Item> {
20        let mut iter = match self.iter.take() {
21            Some(iter) => iter,
22            None => return None,
23        };
24
25        let mut sub_iter = match self.sub_iter.take() {
26            Some(sub_iter) => sub_iter,
27            None => {
28                let item = match iter.next() {
29                    Some(Ok(item)) => item,
30                    Some(Err(err)) => {
31                        return Some(Err(err));
32                    }
33                    None => {
34                        return None;
35                    }
36                };
37                let into_iter = match (self.f)(item) {
38                    Ok(into_iter) => into_iter,
39                    Err(err) => return Some(Err(err)),
40                };
41                into_iter.into_iter()
42            }
43        };
44
45        loop {
46            match sub_iter.next() {
47                Some(item) => {
48                    self.iter = Some(iter);
49                    self.sub_iter = Some(sub_iter);
50                    return Some(Ok(item));
51                }
52                None => {
53                    let item = match iter.next() {
54                        Some(Ok(item)) => item,
55                        Some(Err(err)) => {
56                            return Some(Err(err));
57                        }
58                        None => {
59                            return None;
60                        }
61                    };
62                    let into_iter = match (self.f)(item) {
63                        Ok(into_iter) => into_iter,
64                        Err(err) => return Some(Err(err)),
65                    };
66                    sub_iter = into_iter.into_iter();
67                }
68            }
69        }
70    }
71}
iterator_ext/try_flat_map.rs

iterator_ext/
try_flat_map.rs
