62 lines
2.6 KiB
Rust
62 lines
2.6 KiB
Rust
//! "Diff"ing iterators for caching elements to sequential collections without requiring the new
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//! elements' iterator to be `Clone`.
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//!
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//! - [`Diff`] (produced by the [`diff_with`] function)
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//! describes the difference between two non-`Clone` iterators `I` and `J` after breaking ASAP from
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//! a lock-step comparison.
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use crate::free::put_back;
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use crate::structs::PutBack;
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/// A type returned by the [`diff_with`] function.
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///
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/// `Diff` represents the way in which the elements yielded by the iterator `I` differ to some
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/// iterator `J`.
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pub enum Diff<I, J>
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where I: Iterator,
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J: Iterator
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{
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/// The index of the first non-matching element along with both iterator's remaining elements
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/// starting with the first mis-match.
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FirstMismatch(usize, PutBack<I>, PutBack<J>),
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/// The total number of elements that were in `J` along with the remaining elements of `I`.
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Shorter(usize, PutBack<I>),
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/// The total number of elements that were in `I` along with the remaining elements of `J`.
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Longer(usize, PutBack<J>),
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}
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/// Compares every element yielded by both `i` and `j` with the given function in lock-step and
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/// returns a [`Diff`] which describes how `j` differs from `i`.
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///
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/// If the number of elements yielded by `j` is less than the number of elements yielded by `i`,
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/// the number of `j` elements yielded will be returned along with `i`'s remaining elements as
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/// `Diff::Shorter`.
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///
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/// If the two elements of a step differ, the index of those elements along with the remaining
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/// elements of both `i` and `j` are returned as `Diff::FirstMismatch`.
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///
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/// If `i` becomes exhausted before `j` becomes exhausted, the number of elements in `i` along with
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/// the remaining `j` elements will be returned as `Diff::Longer`.
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pub fn diff_with<I, J, F>(i: I, j: J, is_equal: F)
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-> Option<Diff<I::IntoIter, J::IntoIter>>
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where I: IntoIterator,
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J: IntoIterator,
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F: Fn(&I::Item, &J::Item) -> bool
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{
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let mut i = i.into_iter();
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let mut j = j.into_iter();
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let mut idx = 0;
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while let Some(i_elem) = i.next() {
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match j.next() {
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None => return Some(Diff::Shorter(idx, put_back(i).with_value(i_elem))),
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Some(j_elem) => if !is_equal(&i_elem, &j_elem) {
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let remaining_i = put_back(i).with_value(i_elem);
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let remaining_j = put_back(j).with_value(j_elem);
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return Some(Diff::FirstMismatch(idx, remaining_i, remaining_j));
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},
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}
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idx += 1;
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}
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j.next().map(|j_elem| Diff::Longer(idx, put_back(j).with_value(j_elem)))
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}
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