/rust/registry/src/index.crates.io-1949cf8c6b5b557f/itertools-0.14.0/src/iter_index.rs
Line | Count | Source |
1 | | use core::iter::{Skip, Take}; |
2 | | use core::ops::{Range, RangeFrom, RangeFull, RangeInclusive, RangeTo, RangeToInclusive}; |
3 | | |
4 | | #[cfg(doc)] |
5 | | use crate::Itertools; |
6 | | |
7 | | mod private_iter_index { |
8 | | use core::ops; |
9 | | |
10 | | pub trait Sealed {} |
11 | | |
12 | | impl Sealed for ops::Range<usize> {} |
13 | | impl Sealed for ops::RangeInclusive<usize> {} |
14 | | impl Sealed for ops::RangeTo<usize> {} |
15 | | impl Sealed for ops::RangeToInclusive<usize> {} |
16 | | impl Sealed for ops::RangeFrom<usize> {} |
17 | | impl Sealed for ops::RangeFull {} |
18 | | } |
19 | | |
20 | | /// Used by [`Itertools::get`] to know which iterator |
21 | | /// to turn different ranges into. |
22 | | pub trait IteratorIndex<I>: private_iter_index::Sealed |
23 | | where |
24 | | I: Iterator, |
25 | | { |
26 | | /// The type returned for this type of index. |
27 | | type Output: Iterator<Item = I::Item>; |
28 | | |
29 | | /// Returns an adapted iterator for the current index. |
30 | | /// |
31 | | /// Prefer calling [`Itertools::get`] instead |
32 | | /// of calling this directly. |
33 | | fn index(self, from: I) -> Self::Output; |
34 | | } |
35 | | |
36 | | impl<I> IteratorIndex<I> for Range<usize> |
37 | | where |
38 | | I: Iterator, |
39 | | { |
40 | | type Output = Skip<Take<I>>; |
41 | | |
42 | 0 | fn index(self, iter: I) -> Self::Output { |
43 | 0 | iter.take(self.end).skip(self.start) |
44 | 0 | } |
45 | | } |
46 | | |
47 | | impl<I> IteratorIndex<I> for RangeInclusive<usize> |
48 | | where |
49 | | I: Iterator, |
50 | | { |
51 | | type Output = Take<Skip<I>>; |
52 | | |
53 | 0 | fn index(self, iter: I) -> Self::Output { |
54 | | // end - start + 1 without overflowing if possible |
55 | 0 | let length = if *self.end() == usize::MAX { |
56 | 0 | assert_ne!(*self.start(), 0); |
57 | 0 | self.end() - self.start() + 1 |
58 | | } else { |
59 | 0 | (self.end() + 1).saturating_sub(*self.start()) |
60 | | }; |
61 | 0 | iter.skip(*self.start()).take(length) |
62 | 0 | } |
63 | | } |
64 | | |
65 | | impl<I> IteratorIndex<I> for RangeTo<usize> |
66 | | where |
67 | | I: Iterator, |
68 | | { |
69 | | type Output = Take<I>; |
70 | | |
71 | 0 | fn index(self, iter: I) -> Self::Output { |
72 | 0 | iter.take(self.end) |
73 | 0 | } |
74 | | } |
75 | | |
76 | | impl<I> IteratorIndex<I> for RangeToInclusive<usize> |
77 | | where |
78 | | I: Iterator, |
79 | | { |
80 | | type Output = Take<I>; |
81 | | |
82 | 0 | fn index(self, iter: I) -> Self::Output { |
83 | 0 | assert_ne!(self.end, usize::MAX); |
84 | 0 | iter.take(self.end + 1) |
85 | 0 | } |
86 | | } |
87 | | |
88 | | impl<I> IteratorIndex<I> for RangeFrom<usize> |
89 | | where |
90 | | I: Iterator, |
91 | | { |
92 | | type Output = Skip<I>; |
93 | | |
94 | 0 | fn index(self, iter: I) -> Self::Output { |
95 | 0 | iter.skip(self.start) |
96 | 0 | } |
97 | | } |
98 | | |
99 | | impl<I> IteratorIndex<I> for RangeFull |
100 | | where |
101 | | I: Iterator, |
102 | | { |
103 | | type Output = I; |
104 | | |
105 | 0 | fn index(self, iter: I) -> Self::Output { |
106 | 0 | iter |
107 | 0 | } |
108 | | } |
109 | | |
110 | 0 | pub fn get<I, R>(iter: I, index: R) -> R::Output |
111 | 0 | where |
112 | 0 | I: IntoIterator, |
113 | 0 | R: IteratorIndex<I::IntoIter>, |
114 | | { |
115 | 0 | index.index(iter.into_iter()) |
116 | 0 | } |