1use std::iter::FromIterator;
2use std::marker::PhantomData;
3
4#[derive(Clone, Debug)]
5#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
6pub struct MapSpecialCase<I, F> {
7 iter: I,
8 f: F,
9}
10
11pub trait MapSpecialCaseFn<T> {
12 type Out;
13 fn call(&mut self, t: T) -> Self::Out;
14}
15
16impl<I, R> Iterator for MapSpecialCase<I, R>
17where
18 I: Iterator,
19 R: MapSpecialCaseFn<I::Item>,
20{
21 type Item = R::Out;
22
23 fn next(&mut self) -> Option<Self::Item> {
24 self.iter.next().map(|i| self.f.call(i))
25 }
26
27 fn size_hint(&self) -> (usize, Option<usize>) {
28 self.iter.size_hint()
29 }
30
31 fn fold<Acc, Fold>(self, init: Acc, mut fold_f: Fold) -> Acc
32 where
33 Fold: FnMut(Acc, Self::Item) -> Acc,
34 {
35 let mut f = self.f;
36 self.iter.fold(init, move |acc, v| fold_f(acc, f.call(v)))
37 }
38
39 fn collect<C>(self) -> C
40 where
41 C: FromIterator<Self::Item>,
42 {
43 let mut f = self.f;
44 self.iter.map(move |v| f.call(v)).collect()
45 }
46}
47
48impl<I, R> DoubleEndedIterator for MapSpecialCase<I, R>
49where
50 I: DoubleEndedIterator,
51 R: MapSpecialCaseFn<I::Item>,
52{
53 fn next_back(&mut self) -> Option<Self::Item> {
54 self.iter.next_back().map(|i| self.f.call(i))
55 }
56}
57
58impl<I, R> ExactSizeIterator for MapSpecialCase<I, R>
59where
60 I: ExactSizeIterator,
61 R: MapSpecialCaseFn<I::Item>,
62{
63}
64
65/// An iterator adapter to apply a transformation within a nested `Result::Ok`.
66///
67/// See [`.map_ok()`](crate::Itertools::map_ok) for more information.
68pub type MapOk<I, F> = MapSpecialCase<I, MapSpecialCaseFnOk<F>>;
69
70/// See [`MapOk`].
71#[deprecated(note = "Use MapOk instead", since = "0.10.0")]
72pub type MapResults<I, F> = MapOk<I, F>;
73
74impl<F, T, U, E> MapSpecialCaseFn<Result<T, E>> for MapSpecialCaseFnOk<F>
75where
76 F: FnMut(T) -> U,
77{
78 type Out = Result<U, E>;
79 fn call(&mut self, t: Result<T, E>) -> Self::Out {
80 t.map(|v| self.0(v))
81 }
82}
83
84#[derive(Clone)]
85pub struct MapSpecialCaseFnOk<F>(F);
86
87impl<F> std::fmt::Debug for MapSpecialCaseFnOk<F> {
88 debug_fmt_fields!(MapSpecialCaseFnOk,);
89}
90
91/// Create a new `MapOk` iterator.
92pub fn map_ok<I, F, T, U, E>(iter: I, f: F) -> MapOk<I, F>
93where
94 I: Iterator<Item = Result<T, E>>,
95 F: FnMut(T) -> U,
96{
97 MapSpecialCase {
98 iter,
99 f: MapSpecialCaseFnOk(f),
100 }
101}
102
103/// An iterator adapter to apply `Into` conversion to each element.
104///
105/// See [`.map_into()`](crate::Itertools::map_into) for more information.
106pub type MapInto<I, R> = MapSpecialCase<I, MapSpecialCaseFnInto<R>>;
107
108impl<T: Into<U>, U> MapSpecialCaseFn<T> for MapSpecialCaseFnInto<U> {
109 type Out = U;
110 fn call(&mut self, t: T) -> Self::Out {
111 t.into()
112 }
113}
114
115#[derive(Clone, Debug)]
116pub struct MapSpecialCaseFnInto<U>(PhantomData<U>);
117
118/// Create a new [`MapInto`] iterator.
119pub fn map_into<I, R>(iter: I) -> MapInto<I, R> {
120 MapSpecialCase {
121 iter,
122 f: MapSpecialCaseFnInto(PhantomData),
123 }
124}
125