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1 | //! "Diff"ing iterators for caching elements to sequential collections without requiring the new |
2 | //! elements' iterator to be `Clone`. | |
3 | //! | |
4 | //! - [**Diff**](./enum.Diff.html) (produced by the [**diff_with**](./fn.diff_with.html) function) | |
5 | //! describes the difference between two non-`Clone` iterators `I` and `J` after breaking ASAP from | |
6 | //! a lock-step comparison. | |
7 | ||
72b1a166 FG |
8 | use crate::free::put_back; |
9 | use crate::structs::PutBack; | |
532ac7d7 XL |
10 | |
11 | /// A type returned by the [`diff_with`](./fn.diff_with.html) function. | |
12 | /// | |
13 | /// `Diff` represents the way in which the elements yielded by the iterator `I` differ to some | |
14 | /// iterator `J`. | |
15 | pub enum Diff<I, J> | |
16 | where I: Iterator, | |
17 | J: Iterator | |
18 | { | |
19 | /// The index of the first non-matching element along with both iterator's remaining elements | |
20 | /// starting with the first mis-match. | |
21 | FirstMismatch(usize, PutBack<I>, PutBack<J>), | |
22 | /// The total number of elements that were in `J` along with the remaining elements of `I`. | |
23 | Shorter(usize, PutBack<I>), | |
24 | /// The total number of elements that were in `I` along with the remaining elements of `J`. | |
25 | Longer(usize, PutBack<J>), | |
26 | } | |
27 | ||
28 | /// Compares every element yielded by both `i` and `j` with the given function in lock-step and | |
29 | /// returns a `Diff` which describes how `j` differs from `i`. | |
30 | /// | |
31 | /// If the number of elements yielded by `j` is less than the number of elements yielded by `i`, | |
32 | /// the number of `j` elements yielded will be returned along with `i`'s remaining elements as | |
33 | /// `Diff::Shorter`. | |
34 | /// | |
35 | /// If the two elements of a step differ, the index of those elements along with the remaining | |
36 | /// elements of both `i` and `j` are returned as `Diff::FirstMismatch`. | |
37 | /// | |
38 | /// If `i` becomes exhausted before `j` becomes exhausted, the number of elements in `i` along with | |
39 | /// the remaining `j` elements will be returned as `Diff::Longer`. | |
40 | pub fn diff_with<I, J, F>(i: I, j: J, is_equal: F) | |
41 | -> Option<Diff<I::IntoIter, J::IntoIter>> | |
42 | where I: IntoIterator, | |
43 | J: IntoIterator, | |
44 | F: Fn(&I::Item, &J::Item) -> bool | |
45 | { | |
46 | let mut i = i.into_iter(); | |
47 | let mut j = j.into_iter(); | |
48 | let mut idx = 0; | |
49 | while let Some(i_elem) = i.next() { | |
50 | match j.next() { | |
51 | None => return Some(Diff::Shorter(idx, put_back(i).with_value(i_elem))), | |
52 | Some(j_elem) => if !is_equal(&i_elem, &j_elem) { | |
53 | let remaining_i = put_back(i).with_value(i_elem); | |
54 | let remaining_j = put_back(j).with_value(j_elem); | |
55 | return Some(Diff::FirstMismatch(idx, remaining_i, remaining_j)); | |
56 | }, | |
57 | } | |
58 | idx += 1; | |
59 | } | |
60 | j.next().map(|j_elem| Diff::Longer(idx, put_back(j).with_value(j_elem))) | |
61 | } |