simple_scan/
diff.rs

1use crate::msg;
2use core::{marker::PhantomData, mem};
3
4/// Iterator adapter for item diff tracking.
5///
6/// This struct is created by the [`diff`](crate::IteratorSimpleScanExt::diff)
7/// method on [`IteratorSimpleScanExt`](crate::IteratorSimpleScanExt). See its
8/// documentation for more.
9#[must_use = msg::iter_must_use!()]
10#[derive(Clone)]
11pub struct Diff<I: Iterator, F, D> {
12    iter: I,
13    prev: I::Item,
14    f: F,
15    d: PhantomData<D>,
16}
17
18impl<I, F, D> Diff<I, F, D>
19where
20    I: Iterator,
21{
22    pub(crate) fn new(iter: I, prev: I::Item, f: F) -> Self {
23        Self {
24            iter,
25            prev,
26            f,
27            d: PhantomData,
28        }
29    }
30}
31
32impl<I, F, D> Iterator for Diff<I, F, D>
33where
34    I: Iterator,
35    I::Item: Clone,
36    F: FnMut(I::Item, I::Item) -> D,
37{
38    type Item = D;
39
40    #[inline]
41    fn next(&mut self) -> Option<Self::Item> {
42        let curr = self.iter.next()?;
43        let prev = mem::replace(&mut self.prev, curr.clone());
44        let diff = (self.f)(curr, prev);
45        Some(diff)
46    }
47
48    #[inline]
49    fn size_hint(&self) -> (usize, Option<usize>) {
50        self.iter.size_hint()
51    }
52}
simple_scan/diff.rs

simple_scan/
diff.rs
