| #![cfg(feature = "use_alloc")] |
| |
| use crate::size_hint; |
| use crate::Itertools; |
| |
| use alloc::vec::Vec; |
| |
| #[derive(Clone)] |
| /// An iterator adaptor that iterates over the cartesian product of |
| /// multiple iterators of type `I`. |
| /// |
| /// An iterator element type is `Vec<I>`. |
| /// |
| /// See [`.multi_cartesian_product()`](crate::Itertools::multi_cartesian_product) |
| /// for more information. |
| #[must_use = "iterator adaptors are lazy and do nothing unless consumed"] |
| pub struct MultiProduct<I>(Vec<MultiProductIter<I>>) |
| where I: Iterator + Clone, |
| I::Item: Clone; |
| |
| impl<I> std::fmt::Debug for MultiProduct<I> |
| where |
| I: Iterator + Clone + std::fmt::Debug, |
| I::Item: Clone + std::fmt::Debug, |
| { |
| debug_fmt_fields!(CoalesceBy, 0); |
| } |
| |
| /// Create a new cartesian product iterator over an arbitrary number |
| /// of iterators of the same type. |
| /// |
| /// Iterator element is of type `Vec<H::Item::Item>`. |
| pub fn multi_cartesian_product<H>(iters: H) -> MultiProduct<<H::Item as IntoIterator>::IntoIter> |
| where H: Iterator, |
| H::Item: IntoIterator, |
| <H::Item as IntoIterator>::IntoIter: Clone, |
| <H::Item as IntoIterator>::Item: Clone |
| { |
| MultiProduct(iters.map(|i| MultiProductIter::new(i.into_iter())).collect()) |
| } |
| |
| #[derive(Clone, Debug)] |
| /// Holds the state of a single iterator within a MultiProduct. |
| struct MultiProductIter<I> |
| where I: Iterator + Clone, |
| I::Item: Clone |
| { |
| cur: Option<I::Item>, |
| iter: I, |
| iter_orig: I, |
| } |
| |
| /// Holds the current state during an iteration of a MultiProduct. |
| #[derive(Debug)] |
| enum MultiProductIterState { |
| StartOfIter, |
| MidIter { on_first_iter: bool }, |
| } |
| |
| impl<I> MultiProduct<I> |
| where I: Iterator + Clone, |
| I::Item: Clone |
| { |
| /// Iterates the rightmost iterator, then recursively iterates iterators |
| /// to the left if necessary. |
| /// |
| /// Returns true if the iteration succeeded, else false. |
| fn iterate_last( |
| multi_iters: &mut [MultiProductIter<I>], |
| mut state: MultiProductIterState |
| ) -> bool { |
| use self::MultiProductIterState::*; |
| |
| if let Some((last, rest)) = multi_iters.split_last_mut() { |
| let on_first_iter = match state { |
| StartOfIter => { |
| let on_first_iter = !last.in_progress(); |
| state = MidIter { on_first_iter }; |
| on_first_iter |
| }, |
| MidIter { on_first_iter } => on_first_iter |
| }; |
| |
| if !on_first_iter { |
| last.iterate(); |
| } |
| |
| if last.in_progress() { |
| true |
| } else if MultiProduct::iterate_last(rest, state) { |
| last.reset(); |
| last.iterate(); |
| // If iterator is None twice consecutively, then iterator is |
| // empty; whole product is empty. |
| last.in_progress() |
| } else { |
| false |
| } |
| } else { |
| // Reached end of iterator list. On initialisation, return true. |
| // At end of iteration (final iterator finishes), finish. |
| match state { |
| StartOfIter => false, |
| MidIter { on_first_iter } => on_first_iter |
| } |
| } |
| } |
| |
| /// Returns the unwrapped value of the next iteration. |
| fn curr_iterator(&self) -> Vec<I::Item> { |
| self.0.iter().map(|multi_iter| { |
| multi_iter.cur.clone().unwrap() |
| }).collect() |
| } |
| |
| /// Returns true if iteration has started and has not yet finished; false |
| /// otherwise. |
| fn in_progress(&self) -> bool { |
| if let Some(last) = self.0.last() { |
| last.in_progress() |
| } else { |
| false |
| } |
| } |
| } |
| |
| impl<I> MultiProductIter<I> |
| where I: Iterator + Clone, |
| I::Item: Clone |
| { |
| fn new(iter: I) -> Self { |
| MultiProductIter { |
| cur: None, |
| iter: iter.clone(), |
| iter_orig: iter |
| } |
| } |
| |
| /// Iterate the managed iterator. |
| fn iterate(&mut self) { |
| self.cur = self.iter.next(); |
| } |
| |
| /// Reset the managed iterator. |
| fn reset(&mut self) { |
| self.iter = self.iter_orig.clone(); |
| } |
| |
| /// Returns true if the current iterator has been started and has not yet |
| /// finished; false otherwise. |
| fn in_progress(&self) -> bool { |
| self.cur.is_some() |
| } |
| } |
| |
| impl<I> Iterator for MultiProduct<I> |
| where I: Iterator + Clone, |
| I::Item: Clone |
| { |
| type Item = Vec<I::Item>; |
| |
| fn next(&mut self) -> Option<Self::Item> { |
| if MultiProduct::iterate_last( |
| &mut self.0, |
| MultiProductIterState::StartOfIter |
| ) { |
| Some(self.curr_iterator()) |
| } else { |
| None |
| } |
| } |
| |
| fn count(self) -> usize { |
| if self.0.is_empty() { |
| return 0; |
| } |
| |
| if !self.in_progress() { |
| return self.0.into_iter().fold(1, |acc, multi_iter| { |
| acc * multi_iter.iter.count() |
| }); |
| } |
| |
| self.0.into_iter().fold( |
| 0, |
| |acc, MultiProductIter { iter, iter_orig, cur: _ }| { |
| let total_count = iter_orig.count(); |
| let cur_count = iter.count(); |
| acc * total_count + cur_count |
| } |
| ) |
| } |
| |
| fn size_hint(&self) -> (usize, Option<usize>) { |
| // Not ExactSizeIterator because size may be larger than usize |
| if self.0.is_empty() { |
| return (0, Some(0)); |
| } |
| |
| if !self.in_progress() { |
| return self.0.iter().fold((1, Some(1)), |acc, multi_iter| { |
| size_hint::mul(acc, multi_iter.iter.size_hint()) |
| }); |
| } |
| |
| self.0.iter().fold( |
| (0, Some(0)), |
| |acc, &MultiProductIter { ref iter, ref iter_orig, cur: _ }| { |
| let cur_size = iter.size_hint(); |
| let total_size = iter_orig.size_hint(); |
| size_hint::add(size_hint::mul(acc, total_size), cur_size) |
| } |
| ) |
| } |
| |
| fn last(self) -> Option<Self::Item> { |
| let iter_count = self.0.len(); |
| |
| let lasts: Self::Item = self.0.into_iter() |
| .map(|multi_iter| multi_iter.iter.last()) |
| .while_some() |
| .collect(); |
| |
| if lasts.len() == iter_count { |
| Some(lasts) |
| } else { |
| None |
| } |
| } |
| } |