gat_lending_iterator/adapters/
map.rs

1use crate::{LendingIterator, SingleArgFnMut, SingleArgFnOnce};
2use core::fmt;
3
4/// A lending iterator that maps the elements of `iter` with `f`.
5///
6/// This `struct` is created by the [`map`] method on [`LendingIterator`]. See
7/// its documentation for more.
8///
9/// [`LendingIterator`]: crate::LendingIterator
10/// [`map`]: crate::LendingIterator::map
11#[derive(Clone)]
12#[must_use = "iterators are lazy and do nothing unless consumed"]
13pub struct Map<I, F> {
14    iter: I,
15    f: F,
16}
17
18impl<I, F> Map<I, F> {
19    pub(crate) fn new(iter: I, f: F) -> Self {
20        Self { iter, f }
21    }
22}
23
24impl<I: fmt::Debug, F> fmt::Debug for Map<I, F> {
25    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
26        f.debug_struct("Map")
27            .field("iter", &self.iter)
28            .finish_non_exhaustive()
29    }
30}
31
32impl<I, F> LendingIterator for Map<I, F>
33where
34    I: LendingIterator,
35    F: for<'a> SingleArgFnMut<I::Item<'a>>,
36{
37    type Item<'a>
38        = <F as SingleArgFnOnce<I::Item<'a>>>::Output
39    where
40        Self: 'a;
41
42    #[inline]
43    fn next(&mut self) -> Option<Self::Item<'_>> {
44        self.iter.next().map(&mut self.f)
45    }
46}
47
48/// An iterator that maps the elements of `iter` with `f`.
49///
50/// This `struct` is created when [`IntoIterator::into_iter`] is called on [`Map`].
51pub struct IntoIter<I, F> {
52    iter: I,
53    f: F,
54}
55
56impl<I, F, O> Iterator for IntoIter<I, F>
57where
58    I: LendingIterator,
59    F: FnMut(I::Item<'_>) -> O,
60{
61    type Item = O;
62
63    fn next(&mut self) -> Option<Self::Item> {
64        self.iter.next().map(&mut self.f)
65    }
66}
67
68impl<I, F, O> IntoIterator for Map<I, F>
69where
70    I: LendingIterator,
71    F: FnMut(I::Item<'_>) -> O,
72{
73    type Item = O;
74    type IntoIter = IntoIter<I, F>;
75
76    fn into_iter(self) -> Self::IntoIter {
77        IntoIter {
78            iter: self.iter,
79            f: self.f,
80        }
81    }
82}
83
84#[cfg(test)]
85mod tests {
86    use crate::{LendingIterator, ToLendingIterator};
87
88    fn double(x: i32) -> i32 {
89        x * 2
90    }
91
92    fn extract_second(slice: &[i32]) -> &i32 {
93        &slice[1]
94    }
95
96    #[test]
97    fn map_basic() {
98        let result: Vec<_> = (0..3).into_lending().map(double).into_iter().collect();
99        assert_eq!(result, vec![0, 2, 4]);
100    }
101
102    #[test]
103    fn map_with_borrowing() {
104        let result: Vec<_> = (0..5)
105            .windows(3)
106            .map(extract_second)
107            .cloned()
108            .into_iter()
109            .collect();
110        assert_eq!(result, vec![1, 2, 3]);
111    }
112}
gat_lending_iterator/adapters/map.rs

gat_lending_iterator/adapters/
map.rs
