zaplib_vector/internal_iter/
internal_iterator.rs

1/// A trait for internal iterators. An internal iterator differs from a normal iterator in that its
2/// iteration is controlled internally by the iterator itself, instead of externally by the calling
3/// code. This means that instead of returning a single item on each call to `next`, internal
4/// iterators call a closure for each item on a single call to `for_each`. This allows internal
5/// operators to be implemented recursively, something that is not possible with normal iterators.
6pub trait InternalIterator {
7    type Item;
8
9    /// Calls `f` with each item of `self`.
10    ///
11    /// If `f` returns `false`, iteration is aborted. If iteration was aborted, this function
12    /// returns `false`.
13    fn for_each<F>(self, f: &mut F) -> bool
14    where
15        F: FnMut(Self::Item) -> bool;
16
17    /// Returns an internal iterator that applies `f` to each item of `self`.
18    fn map<R, F>(self, f: F) -> Map<Self, F>
19    where
20        Self: Sized,
21        F: FnMut(Self::Item) -> R,
22    {
23        Map { internal_iter: self, f }
24    }
25}
26
27impl<I> InternalIterator for I
28where
29    I: Iterator,
30{
31    type Item = I::Item;
32
33    fn for_each<F>(self, f: &mut F) -> bool
34    where
35        F: FnMut(Self::Item) -> bool,
36    {
37        for item in self {
38            if !f(item) {
39                return false;
40            }
41        }
42        true
43    }
44}
45
46/// An internal iterator that applies `f` to each item of `self`.
47#[derive(Clone, Debug)]
48pub struct Map<I, F> {
49    internal_iter: I,
50    f: F,
51}
52
53impl<R, I, F> InternalIterator for Map<I, F>
54where
55    I: InternalIterator,
56    F: FnMut(I::Item) -> R,
57{
58    type Item = R;
59
60    fn for_each<G>(mut self, g: &mut G) -> bool
61    where
62        G: FnMut(Self::Item) -> bool,
63    {
64        self.internal_iter.for_each({
65            let f = &mut self.f;
66            &mut move |item| g((f)(item))
67        })
68    }
69}
zaplib_vector/internal_iter/internal_iterator.rs

zaplib_vector/internal_iter/
internal_iterator.rs
