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