itertools/
process_results_impl.rs

1#[cfg(doc)]
2use crate::Itertools;
3
4/// An iterator that produces only the `T` values as long as the
5/// inner iterator produces `Ok(T)`.
6///
7/// Used by [`process_results`](crate::process_results), see its docs
8/// for more information.
9#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
10#[derive(Debug)]
11pub struct ProcessResults<'a, I, E: 'a> {
12    error: &'a mut Result<(), E>,
13    iter: I,
14}
15
16impl<'a, I, T, E> Iterator for ProcessResults<'a, I, E>
17where
18    I: Iterator<Item = Result<T, E>>,
19{
20    type Item = T;
21
22    fn next(&mut self) -> Option<Self::Item> {
23        match self.iter.next() {
24            Some(Ok(x)) => Some(x),
25            Some(Err(e)) => {
26                *self.error = Err(e);
27                None
28            }
29            None => None,
30        }
31    }
32
33    fn size_hint(&self) -> (usize, Option<usize>) {
34        (0, self.iter.size_hint().1)
35    }
36
37    fn fold<B, F>(mut self, init: B, mut f: F) -> B
38    where
39        Self: Sized,
40        F: FnMut(B, Self::Item) -> B,
41    {
42        let error = self.error;
43        self.iter
44            .try_fold(init, |acc, opt| match opt {
45                Ok(x) => Ok(f(acc, x)),
46                Err(e) => {
47                    *error = Err(e);
48                    Err(acc)
49                }
50            })
51            .unwrap_or_else(|e| e)
52    }
53}
54
55/// “Lift” a function of the values of an iterator so that it can process
56/// an iterator of `Result` values instead.
57///
58/// [`IntoIterator`] enabled version of [`Itertools::process_results`].
59pub fn process_results<I, F, T, E, R>(iterable: I, processor: F) -> Result<R, E>
60where
61    I: IntoIterator<Item = Result<T, E>>,
62    F: FnOnce(ProcessResults<I::IntoIter, E>) -> R,
63{
64    let iter = iterable.into_iter();
65    let mut error = Ok(());
66
67    let result = processor(ProcessResults {
68        error: &mut error,
69        iter,
70    });
71
72    error.map(|_| result)
73}
itertools/process_results_impl.rs

itertools/
process_results_impl.rs
