Jakub Kotur | a425e55 | 2020-12-21 17:28:15 +0100 | [diff] [blame] | 1 | |
| 2 | use std::collections::HashMap; |
| 3 | use std::collections::hash_map::{Entry}; |
| 4 | use std::hash::Hash; |
| 5 | use std::fmt; |
| 6 | |
| 7 | /// An iterator adapter to filter out duplicate elements. |
| 8 | /// |
| 9 | /// See [`.unique_by()`](../trait.Itertools.html#method.unique) for more information. |
| 10 | #[derive(Clone)] |
| 11 | #[must_use = "iterator adaptors are lazy and do nothing unless consumed"] |
| 12 | pub struct UniqueBy<I: Iterator, V, F> { |
| 13 | iter: I, |
| 14 | // Use a hashmap for the entry API |
| 15 | used: HashMap<V, ()>, |
| 16 | f: F, |
| 17 | } |
| 18 | |
| 19 | impl<I, V, F> fmt::Debug for UniqueBy<I, V, F> |
| 20 | where I: Iterator + fmt::Debug, |
| 21 | V: fmt::Debug + Hash + Eq, |
| 22 | { |
| 23 | debug_fmt_fields!(UniqueBy, iter, used); |
| 24 | } |
| 25 | |
| 26 | /// Create a new `UniqueBy` iterator. |
| 27 | pub fn unique_by<I, V, F>(iter: I, f: F) -> UniqueBy<I, V, F> |
| 28 | where V: Eq + Hash, |
| 29 | F: FnMut(&I::Item) -> V, |
| 30 | I: Iterator, |
| 31 | { |
| 32 | UniqueBy { |
| 33 | iter, |
| 34 | used: HashMap::new(), |
| 35 | f, |
| 36 | } |
| 37 | } |
| 38 | |
| 39 | // count the number of new unique keys in iterable (`used` is the set already seen) |
| 40 | fn count_new_keys<I, K>(mut used: HashMap<K, ()>, iterable: I) -> usize |
| 41 | where I: IntoIterator<Item=K>, |
| 42 | K: Hash + Eq, |
| 43 | { |
| 44 | let iter = iterable.into_iter(); |
| 45 | let current_used = used.len(); |
| 46 | used.extend(iter.map(|key| (key, ()))); |
| 47 | used.len() - current_used |
| 48 | } |
| 49 | |
| 50 | impl<I, V, F> Iterator for UniqueBy<I, V, F> |
| 51 | where I: Iterator, |
| 52 | V: Eq + Hash, |
| 53 | F: FnMut(&I::Item) -> V |
| 54 | { |
| 55 | type Item = I::Item; |
| 56 | |
Joel Galenson | 6f79871 | 2021-04-01 17:03:06 -0700 | [diff] [blame] | 57 | fn next(&mut self) -> Option<Self::Item> { |
Jakub Kotur | a425e55 | 2020-12-21 17:28:15 +0100 | [diff] [blame] | 58 | while let Some(v) = self.iter.next() { |
| 59 | let key = (self.f)(&v); |
| 60 | if self.used.insert(key, ()).is_none() { |
| 61 | return Some(v); |
| 62 | } |
| 63 | } |
| 64 | None |
| 65 | } |
| 66 | |
| 67 | #[inline] |
| 68 | fn size_hint(&self) -> (usize, Option<usize>) { |
| 69 | let (low, hi) = self.iter.size_hint(); |
| 70 | ((low > 0 && self.used.is_empty()) as usize, hi) |
| 71 | } |
| 72 | |
| 73 | fn count(self) -> usize { |
| 74 | let mut key_f = self.f; |
| 75 | count_new_keys(self.used, self.iter.map(move |elt| key_f(&elt))) |
| 76 | } |
| 77 | } |
| 78 | |
Joel Galenson | 6f79871 | 2021-04-01 17:03:06 -0700 | [diff] [blame] | 79 | impl<I, V, F> DoubleEndedIterator for UniqueBy<I, V, F> |
| 80 | where I: DoubleEndedIterator, |
| 81 | V: Eq + Hash, |
| 82 | F: FnMut(&I::Item) -> V |
| 83 | { |
| 84 | fn next_back(&mut self) -> Option<Self::Item> { |
| 85 | while let Some(v) = self.iter.next_back() { |
| 86 | let key = (self.f)(&v); |
| 87 | if self.used.insert(key, ()).is_none() { |
| 88 | return Some(v); |
| 89 | } |
| 90 | } |
| 91 | None |
| 92 | } |
| 93 | } |
| 94 | |
Jakub Kotur | a425e55 | 2020-12-21 17:28:15 +0100 | [diff] [blame] | 95 | impl<I> Iterator for Unique<I> |
| 96 | where I: Iterator, |
| 97 | I::Item: Eq + Hash + Clone |
| 98 | { |
| 99 | type Item = I::Item; |
| 100 | |
Joel Galenson | 6f79871 | 2021-04-01 17:03:06 -0700 | [diff] [blame] | 101 | fn next(&mut self) -> Option<Self::Item> { |
Jakub Kotur | a425e55 | 2020-12-21 17:28:15 +0100 | [diff] [blame] | 102 | while let Some(v) = self.iter.iter.next() { |
| 103 | if let Entry::Vacant(entry) = self.iter.used.entry(v) { |
| 104 | let elt = entry.key().clone(); |
| 105 | entry.insert(()); |
| 106 | return Some(elt); |
| 107 | } |
| 108 | } |
| 109 | None |
| 110 | } |
| 111 | |
| 112 | #[inline] |
| 113 | fn size_hint(&self) -> (usize, Option<usize>) { |
| 114 | let (low, hi) = self.iter.iter.size_hint(); |
| 115 | ((low > 0 && self.iter.used.is_empty()) as usize, hi) |
| 116 | } |
| 117 | |
| 118 | fn count(self) -> usize { |
| 119 | count_new_keys(self.iter.used, self.iter.iter) |
| 120 | } |
| 121 | } |
| 122 | |
Joel Galenson | 6f79871 | 2021-04-01 17:03:06 -0700 | [diff] [blame] | 123 | impl<I> DoubleEndedIterator for Unique<I> |
| 124 | where I: DoubleEndedIterator, |
| 125 | I::Item: Eq + Hash + Clone |
| 126 | { |
| 127 | fn next_back(&mut self) -> Option<Self::Item> { |
| 128 | while let Some(v) = self.iter.iter.next_back() { |
| 129 | if let Entry::Vacant(entry) = self.iter.used.entry(v) { |
| 130 | let elt = entry.key().clone(); |
| 131 | entry.insert(()); |
| 132 | return Some(elt); |
| 133 | } |
| 134 | } |
| 135 | None |
| 136 | } |
| 137 | } |
| 138 | |
Jakub Kotur | a425e55 | 2020-12-21 17:28:15 +0100 | [diff] [blame] | 139 | /// An iterator adapter to filter out duplicate elements. |
| 140 | /// |
| 141 | /// See [`.unique()`](../trait.Itertools.html#method.unique) for more information. |
| 142 | #[derive(Clone)] |
| 143 | #[must_use = "iterator adaptors are lazy and do nothing unless consumed"] |
| 144 | pub struct Unique<I: Iterator> { |
| 145 | iter: UniqueBy<I, I::Item, ()>, |
| 146 | } |
| 147 | |
| 148 | impl<I> fmt::Debug for Unique<I> |
| 149 | where I: Iterator + fmt::Debug, |
| 150 | I::Item: Hash + Eq + fmt::Debug, |
| 151 | { |
| 152 | debug_fmt_fields!(Unique, iter); |
| 153 | } |
| 154 | |
| 155 | pub fn unique<I>(iter: I) -> Unique<I> |
| 156 | where I: Iterator, |
| 157 | I::Item: Eq + Hash, |
| 158 | { |
| 159 | Unique { |
| 160 | iter: UniqueBy { |
| 161 | iter, |
| 162 | used: HashMap::new(), |
| 163 | f: (), |
| 164 | } |
| 165 | } |
| 166 | } |