Jakub Kotur | a425e55 | 2020-12-21 17:28:15 +0100 | [diff] [blame] | 1 | //! "Diff"ing iterators for caching elements to sequential collections without requiring the new |
| 2 | //! elements' iterator to be `Clone`. |
| 3 | //! |
Joel Galenson | b593e25 | 2021-06-21 13:15:57 -0700 | [diff] [blame] | 4 | //! - [`Diff`] (produced by the [`diff_with`] function) |
Jakub Kotur | a425e55 | 2020-12-21 17:28:15 +0100 | [diff] [blame] | 5 | //! describes the difference between two non-`Clone` iterators `I` and `J` after breaking ASAP from |
| 6 | //! a lock-step comparison. |
| 7 | |
| 8 | use crate::free::put_back; |
| 9 | use crate::structs::PutBack; |
| 10 | |
Joel Galenson | b593e25 | 2021-06-21 13:15:57 -0700 | [diff] [blame] | 11 | /// A type returned by the [`diff_with`] function. |
Jakub Kotur | a425e55 | 2020-12-21 17:28:15 +0100 | [diff] [blame] | 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 |
Joel Galenson | b593e25 | 2021-06-21 13:15:57 -0700 | [diff] [blame] | 29 | /// returns a [`Diff`] which describes how `j` differs from `i`. |
Jakub Kotur | a425e55 | 2020-12-21 17:28:15 +0100 | [diff] [blame] | 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 | } |