itertools/adaptors/
map.rs

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
use std::iter::FromIterator;
use std::marker::PhantomData;

#[derive(Clone, Debug)]
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
pub struct MapSpecialCase<I, F> {
    pub(crate) iter: I,
    pub(crate) f: F,
}

pub trait MapSpecialCaseFn<T> {
    type Out;
    fn call(&mut self, t: T) -> Self::Out;
}

impl<I, R> Iterator for MapSpecialCase<I, R>
where
    I: Iterator,
    R: MapSpecialCaseFn<I::Item>,
{
    type Item = R::Out;

    fn next(&mut self) -> Option<Self::Item> {
        self.iter.next().map(|i| self.f.call(i))
    }

    fn size_hint(&self) -> (usize, Option<usize>) {
        self.iter.size_hint()
    }

    fn fold<Acc, Fold>(self, init: Acc, mut fold_f: Fold) -> Acc
    where
        Fold: FnMut(Acc, Self::Item) -> Acc,
    {
        let mut f = self.f;
        self.iter.fold(init, move |acc, v| fold_f(acc, f.call(v)))
    }

    fn collect<C>(self) -> C
    where
        C: FromIterator<Self::Item>,
    {
        let mut f = self.f;
        self.iter.map(move |v| f.call(v)).collect()
    }
}

impl<I, R> DoubleEndedIterator for MapSpecialCase<I, R>
where
    I: DoubleEndedIterator,
    R: MapSpecialCaseFn<I::Item>,
{
    fn next_back(&mut self) -> Option<Self::Item> {
        self.iter.next_back().map(|i| self.f.call(i))
    }
}

impl<I, R> ExactSizeIterator for MapSpecialCase<I, R>
where
    I: ExactSizeIterator,
    R: MapSpecialCaseFn<I::Item>,
{
}

/// An iterator adapter to apply a transformation within a nested `Result::Ok`.
///
/// See [`.map_ok()`](crate::Itertools::map_ok) for more information.
pub type MapOk<I, F> = MapSpecialCase<I, MapSpecialCaseFnOk<F>>;

impl<F, T, U, E> MapSpecialCaseFn<Result<T, E>> for MapSpecialCaseFnOk<F>
where
    F: FnMut(T) -> U,
{
    type Out = Result<U, E>;
    fn call(&mut self, t: Result<T, E>) -> Self::Out {
        t.map(|v| self.0(v))
    }
}

#[derive(Clone)]
pub struct MapSpecialCaseFnOk<F>(F);

impl<F> std::fmt::Debug for MapSpecialCaseFnOk<F> {
    debug_fmt_fields!(MapSpecialCaseFnOk,);
}

/// Create a new `MapOk` iterator.
pub fn map_ok<I, F, T, U, E>(iter: I, f: F) -> MapOk<I, F>
where
    I: Iterator<Item = Result<T, E>>,
    F: FnMut(T) -> U,
{
    MapSpecialCase {
        iter,
        f: MapSpecialCaseFnOk(f),
    }
}

/// An iterator adapter to apply `Into` conversion to each element.
///
/// See [`.map_into()`](crate::Itertools::map_into) for more information.
pub type MapInto<I, R> = MapSpecialCase<I, MapSpecialCaseFnInto<R>>;

impl<T: Into<U>, U> MapSpecialCaseFn<T> for MapSpecialCaseFnInto<U> {
    type Out = U;
    fn call(&mut self, t: T) -> Self::Out {
        t.into()
    }
}

pub struct MapSpecialCaseFnInto<U>(PhantomData<U>);

impl<U> std::fmt::Debug for MapSpecialCaseFnInto<U> {
    debug_fmt_fields!(MapSpecialCaseFnInto, 0);
}

impl<U> Clone for MapSpecialCaseFnInto<U> {
    #[inline]
    fn clone(&self) -> Self {
        Self(PhantomData)
    }
}

/// Create a new [`MapInto`] iterator.
pub fn map_into<I, R>(iter: I) -> MapInto<I, R> {
    MapSpecialCase {
        iter,
        f: MapSpecialCaseFnInto(PhantomData),
    }
}