1//! [`IndexMap`] is a hash table where the iteration order of the key-value
2//! pairs is independent of the hash values of the keys.
3
4mod core;
5mod iter;
6mod mutable;
7mod slice;
8
9#[cfg(feature = "serde")]
10#[cfg_attr(docsrs, doc(cfg(feature = "serde")))]
11pub mod serde_seq;
12
13#[cfg(test)]
14mod tests;
15
16pub use self::core::raw_entry_v1::{self, RawEntryApiV1};
17pub use self::core::{Entry, IndexedEntry, OccupiedEntry, VacantEntry};
18pub use self::iter::{
19 Drain, IntoIter, IntoKeys, IntoValues, Iter, IterMut, IterMut2, Keys, Splice, Values, ValuesMut,
20};
21pub use self::mutable::MutableEntryKey;
22pub use self::mutable::MutableKeys;
23pub use self::slice::Slice;
24
25#[cfg(feature = "rayon")]
26pub use crate::rayon::map as rayon;
27
28use ::core::cmp::Ordering;
29use ::core::fmt;
30use ::core::hash::{BuildHasher, Hash, Hasher};
31use ::core::mem;
32use ::core::ops::{Index, IndexMut, RangeBounds};
33use alloc::boxed::Box;
34use alloc::vec::Vec;
35
36#[cfg(feature = "std")]
37use std::collections::hash_map::RandomState;
38
39use self::core::IndexMapCore;
40use crate::util::{third, try_simplify_range};
41use crate::{Bucket, Entries, Equivalent, HashValue, TryReserveError};
42
43/// A hash table where the iteration order of the key-value pairs is independent
44/// of the hash values of the keys.
45///
46/// The interface is closely compatible with the standard
47/// [`HashMap`][std::collections::HashMap],
48/// but also has additional features.
49///
50/// # Order
51///
52/// The key-value pairs have a consistent order that is determined by
53/// the sequence of insertion and removal calls on the map. The order does
54/// not depend on the keys or the hash function at all.
55///
56/// All iterators traverse the map in *the order*.
57///
58/// The insertion order is preserved, with **notable exceptions** like the
59/// [`.remove()`][Self::remove] or [`.swap_remove()`][Self::swap_remove] methods.
60/// Methods such as [`.sort_by()`][Self::sort_by] of
61/// course result in a new order, depending on the sorting order.
62///
63/// # Indices
64///
65/// The key-value pairs are indexed in a compact range without holes in the
66/// range `0..self.len()`. For example, the method `.get_full` looks up the
67/// index for a key, and the method `.get_index` looks up the key-value pair by
68/// index.
69///
70/// # Examples
71///
72/// ```
73/// use indexmap::IndexMap;
74///
75/// // count the frequency of each letter in a sentence.
76/// let mut letters = IndexMap::new();
77/// for ch in "a short treatise on fungi".chars() {
78/// *letters.entry(ch).or_insert(0) += 1;
79/// }
80///
81/// assert_eq!(letters[&'s'], 2);
82/// assert_eq!(letters[&'t'], 3);
83/// assert_eq!(letters[&'u'], 1);
84/// assert_eq!(letters.get(&'y'), None);
85/// ```
86#[cfg(feature = "std")]
87pub struct IndexMap<K, V, S = RandomState> {
88 pub(crate) core: IndexMapCore<K, V>,
89 hash_builder: S,
90}
91#[cfg(not(feature = "std"))]
92pub struct IndexMap<K, V, S> {
93 pub(crate) core: IndexMapCore<K, V>,
94 hash_builder: S,
95}
96
97impl<K, V, S> Clone for IndexMap<K, V, S>
98where
99 K: Clone,
100 V: Clone,
101 S: Clone,
102{
103 fn clone(&self) -> Self {
104 IndexMap {
105 core: self.core.clone(),
106 hash_builder: self.hash_builder.clone(),
107 }
108 }
109
110 fn clone_from(&mut self, other: &Self) {
111 self.core.clone_from(&other.core);
112 self.hash_builder.clone_from(&other.hash_builder);
113 }
114}
115
116impl<K, V, S> Entries for IndexMap<K, V, S> {
117 type Entry = Bucket<K, V>;
118
119 #[inline]
120 fn into_entries(self) -> Vec<Self::Entry> {
121 self.core.into_entries()
122 }
123
124 #[inline]
125 fn as_entries(&self) -> &[Self::Entry] {
126 self.core.as_entries()
127 }
128
129 #[inline]
130 fn as_entries_mut(&mut self) -> &mut [Self::Entry] {
131 self.core.as_entries_mut()
132 }
133
134 fn with_entries<F>(&mut self, f: F)
135 where
136 F: FnOnce(&mut [Self::Entry]),
137 {
138 self.core.with_entries(f);
139 }
140}
141
142impl<K, V, S> fmt::Debug for IndexMap<K, V, S>
143where
144 K: fmt::Debug,
145 V: fmt::Debug,
146{
147 #[cfg(not(feature = "test_debug"))]
148 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
149 f.debug_map().entries(self.iter()).finish()
150 }
151
152 #[cfg(feature = "test_debug")]
153 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
154 // Let the inner `IndexMapCore` print all of its details
155 f.debug_struct("IndexMap")
156 .field("core", &self.core)
157 .finish()
158 }
159}
160
161#[cfg(feature = "std")]
162#[cfg_attr(docsrs, doc(cfg(feature = "std")))]
163impl<K, V> IndexMap<K, V> {
164 /// Create a new map. (Does not allocate.)
165 #[inline]
166 pub fn new() -> Self {
167 Self::with_capacity(0)
168 }
169
170 /// Create a new map with capacity for `n` key-value pairs. (Does not
171 /// allocate if `n` is zero.)
172 ///
173 /// Computes in **O(n)** time.
174 #[inline]
175 pub fn with_capacity(n: usize) -> Self {
176 Self::with_capacity_and_hasher(n, <_>::default())
177 }
178}
179
180impl<K, V, S> IndexMap<K, V, S> {
181 /// Create a new map with capacity for `n` key-value pairs. (Does not
182 /// allocate if `n` is zero.)
183 ///
184 /// Computes in **O(n)** time.
185 #[inline]
186 pub fn with_capacity_and_hasher(n: usize, hash_builder: S) -> Self {
187 if n == 0 {
188 Self::with_hasher(hash_builder)
189 } else {
190 IndexMap {
191 core: IndexMapCore::with_capacity(n),
192 hash_builder,
193 }
194 }
195 }
196
197 /// Create a new map with `hash_builder`.
198 ///
199 /// This function is `const`, so it
200 /// can be called in `static` contexts.
201 pub const fn with_hasher(hash_builder: S) -> Self {
202 IndexMap {
203 core: IndexMapCore::new(),
204 hash_builder,
205 }
206 }
207
208 /// Return the number of elements the map can hold without reallocating.
209 ///
210 /// This number is a lower bound; the map might be able to hold more,
211 /// but is guaranteed to be able to hold at least this many.
212 ///
213 /// Computes in **O(1)** time.
214 pub fn capacity(&self) -> usize {
215 self.core.capacity()
216 }
217
218 /// Return a reference to the map's `BuildHasher`.
219 pub fn hasher(&self) -> &S {
220 &self.hash_builder
221 }
222
223 /// Return the number of key-value pairs in the map.
224 ///
225 /// Computes in **O(1)** time.
226 #[inline]
227 pub fn len(&self) -> usize {
228 self.core.len()
229 }
230
231 /// Returns true if the map contains no elements.
232 ///
233 /// Computes in **O(1)** time.
234 #[inline]
235 pub fn is_empty(&self) -> bool {
236 self.len() == 0
237 }
238
239 /// Return an iterator over the key-value pairs of the map, in their order
240 pub fn iter(&self) -> Iter<'_, K, V> {
241 Iter::new(self.as_entries())
242 }
243
244 /// Return an iterator over the key-value pairs of the map, in their order
245 pub fn iter_mut(&mut self) -> IterMut<'_, K, V> {
246 IterMut::new(self.as_entries_mut())
247 }
248
249 /// Return an iterator over the keys of the map, in their order
250 pub fn keys(&self) -> Keys<'_, K, V> {
251 Keys::new(self.as_entries())
252 }
253
254 /// Return an owning iterator over the keys of the map, in their order
255 pub fn into_keys(self) -> IntoKeys<K, V> {
256 IntoKeys::new(self.into_entries())
257 }
258
259 /// Return an iterator over the values of the map, in their order
260 pub fn values(&self) -> Values<'_, K, V> {
261 Values::new(self.as_entries())
262 }
263
264 /// Return an iterator over mutable references to the values of the map,
265 /// in their order
266 pub fn values_mut(&mut self) -> ValuesMut<'_, K, V> {
267 ValuesMut::new(self.as_entries_mut())
268 }
269
270 /// Return an owning iterator over the values of the map, in their order
271 pub fn into_values(self) -> IntoValues<K, V> {
272 IntoValues::new(self.into_entries())
273 }
274
275 /// Remove all key-value pairs in the map, while preserving its capacity.
276 ///
277 /// Computes in **O(n)** time.
278 pub fn clear(&mut self) {
279 self.core.clear();
280 }
281
282 /// Shortens the map, keeping the first `len` elements and dropping the rest.
283 ///
284 /// If `len` is greater than the map's current length, this has no effect.
285 pub fn truncate(&mut self, len: usize) {
286 self.core.truncate(len);
287 }
288
289 /// Clears the `IndexMap` in the given index range, returning those
290 /// key-value pairs as a drain iterator.
291 ///
292 /// The range may be any type that implements [`RangeBounds<usize>`],
293 /// including all of the `std::ops::Range*` types, or even a tuple pair of
294 /// `Bound` start and end values. To drain the map entirely, use `RangeFull`
295 /// like `map.drain(..)`.
296 ///
297 /// This shifts down all entries following the drained range to fill the
298 /// gap, and keeps the allocated memory for reuse.
299 ///
300 /// ***Panics*** if the starting point is greater than the end point or if
301 /// the end point is greater than the length of the map.
302 pub fn drain<R>(&mut self, range: R) -> Drain<'_, K, V>
303 where
304 R: RangeBounds<usize>,
305 {
306 Drain::new(self.core.drain(range))
307 }
308
309 /// Splits the collection into two at the given index.
310 ///
311 /// Returns a newly allocated map containing the elements in the range
312 /// `[at, len)`. After the call, the original map will be left containing
313 /// the elements `[0, at)` with its previous capacity unchanged.
314 ///
315 /// ***Panics*** if `at > len`.
316 pub fn split_off(&mut self, at: usize) -> Self
317 where
318 S: Clone,
319 {
320 Self {
321 core: self.core.split_off(at),
322 hash_builder: self.hash_builder.clone(),
323 }
324 }
325
326 /// Reserve capacity for `additional` more key-value pairs.
327 ///
328 /// Computes in **O(n)** time.
329 pub fn reserve(&mut self, additional: usize) {
330 self.core.reserve(additional);
331 }
332
333 /// Reserve capacity for `additional` more key-value pairs, without over-allocating.
334 ///
335 /// Unlike `reserve`, this does not deliberately over-allocate the entry capacity to avoid
336 /// frequent re-allocations. However, the underlying data structures may still have internal
337 /// capacity requirements, and the allocator itself may give more space than requested, so this
338 /// cannot be relied upon to be precisely minimal.
339 ///
340 /// Computes in **O(n)** time.
341 pub fn reserve_exact(&mut self, additional: usize) {
342 self.core.reserve_exact(additional);
343 }
344
345 /// Try to reserve capacity for `additional` more key-value pairs.
346 ///
347 /// Computes in **O(n)** time.
348 pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError> {
349 self.core.try_reserve(additional)
350 }
351
352 /// Try to reserve capacity for `additional` more key-value pairs, without over-allocating.
353 ///
354 /// Unlike `try_reserve`, this does not deliberately over-allocate the entry capacity to avoid
355 /// frequent re-allocations. However, the underlying data structures may still have internal
356 /// capacity requirements, and the allocator itself may give more space than requested, so this
357 /// cannot be relied upon to be precisely minimal.
358 ///
359 /// Computes in **O(n)** time.
360 pub fn try_reserve_exact(&mut self, additional: usize) -> Result<(), TryReserveError> {
361 self.core.try_reserve_exact(additional)
362 }
363
364 /// Shrink the capacity of the map as much as possible.
365 ///
366 /// Computes in **O(n)** time.
367 pub fn shrink_to_fit(&mut self) {
368 self.core.shrink_to(0);
369 }
370
371 /// Shrink the capacity of the map with a lower limit.
372 ///
373 /// Computes in **O(n)** time.
374 pub fn shrink_to(&mut self, min_capacity: usize) {
375 self.core.shrink_to(min_capacity);
376 }
377}
378
379impl<K, V, S> IndexMap<K, V, S>
380where
381 K: Hash + Eq,
382 S: BuildHasher,
383{
384 /// Insert a key-value pair in the map.
385 ///
386 /// If an equivalent key already exists in the map: the key remains and
387 /// retains in its place in the order, its corresponding value is updated
388 /// with `value`, and the older value is returned inside `Some(_)`.
389 ///
390 /// If no equivalent key existed in the map: the new key-value pair is
391 /// inserted, last in order, and `None` is returned.
392 ///
393 /// Computes in **O(1)** time (amortized average).
394 ///
395 /// See also [`entry`][Self::entry] if you want to insert *or* modify,
396 /// or [`insert_full`][Self::insert_full] if you need to get the index of
397 /// the corresponding key-value pair.
398 pub fn insert(&mut self, key: K, value: V) -> Option<V> {
399 self.insert_full(key, value).1
400 }
401
402 /// Insert a key-value pair in the map, and get their index.
403 ///
404 /// If an equivalent key already exists in the map: the key remains and
405 /// retains in its place in the order, its corresponding value is updated
406 /// with `value`, and the older value is returned inside `(index, Some(_))`.
407 ///
408 /// If no equivalent key existed in the map: the new key-value pair is
409 /// inserted, last in order, and `(index, None)` is returned.
410 ///
411 /// Computes in **O(1)** time (amortized average).
412 ///
413 /// See also [`entry`][Self::entry] if you want to insert *or* modify.
414 pub fn insert_full(&mut self, key: K, value: V) -> (usize, Option<V>) {
415 let hash = self.hash(&key);
416 self.core.insert_full(hash, key, value)
417 }
418
419 /// Insert a key-value pair in the map at its ordered position among sorted keys.
420 ///
421 /// This is equivalent to finding the position with
422 /// [`binary_search_keys`][Self::binary_search_keys], then either updating
423 /// it or calling [`insert_before`][Self::insert_before] for a new key.
424 ///
425 /// If the sorted key is found in the map, its corresponding value is
426 /// updated with `value`, and the older value is returned inside
427 /// `(index, Some(_))`. Otherwise, the new key-value pair is inserted at
428 /// the sorted position, and `(index, None)` is returned.
429 ///
430 /// If the existing keys are **not** already sorted, then the insertion
431 /// index is unspecified (like [`slice::binary_search`]), but the key-value
432 /// pair is moved to or inserted at that position regardless.
433 ///
434 /// Computes in **O(n)** time (average). Instead of repeating calls to
435 /// `insert_sorted`, it may be faster to call batched [`insert`][Self::insert]
436 /// or [`extend`][Self::extend] and only call [`sort_keys`][Self::sort_keys]
437 /// or [`sort_unstable_keys`][Self::sort_unstable_keys] once.
438 pub fn insert_sorted(&mut self, key: K, value: V) -> (usize, Option<V>)
439 where
440 K: Ord,
441 {
442 match self.binary_search_keys(&key) {
443 Ok(i) => (i, Some(mem::replace(&mut self[i], value))),
444 Err(i) => self.insert_before(i, key, value),
445 }
446 }
447
448 /// Insert a key-value pair in the map before the entry at the given index, or at the end.
449 ///
450 /// If an equivalent key already exists in the map: the key remains and
451 /// is moved to the new position in the map, its corresponding value is updated
452 /// with `value`, and the older value is returned inside `Some(_)`. The returned index
453 /// will either be the given index or one less, depending on how the entry moved.
454 /// (See [`shift_insert`](Self::shift_insert) for different behavior here.)
455 ///
456 /// If no equivalent key existed in the map: the new key-value pair is
457 /// inserted exactly at the given index, and `None` is returned.
458 ///
459 /// ***Panics*** if `index` is out of bounds.
460 /// Valid indices are `0..=map.len()` (inclusive).
461 ///
462 /// Computes in **O(n)** time (average).
463 ///
464 /// See also [`entry`][Self::entry] if you want to insert *or* modify,
465 /// perhaps only using the index for new entries with [`VacantEntry::shift_insert`].
466 ///
467 /// # Examples
468 ///
469 /// ```
470 /// use indexmap::IndexMap;
471 /// let mut map: IndexMap<char, ()> = ('a'..='z').map(|c| (c, ())).collect();
472 ///
473 /// // The new key '*' goes exactly at the given index.
474 /// assert_eq!(map.get_index_of(&'*'), None);
475 /// assert_eq!(map.insert_before(10, '*', ()), (10, None));
476 /// assert_eq!(map.get_index_of(&'*'), Some(10));
477 ///
478 /// // Moving the key 'a' up will shift others down, so this moves *before* 10 to index 9.
479 /// assert_eq!(map.insert_before(10, 'a', ()), (9, Some(())));
480 /// assert_eq!(map.get_index_of(&'a'), Some(9));
481 /// assert_eq!(map.get_index_of(&'*'), Some(10));
482 ///
483 /// // Moving the key 'z' down will shift others up, so this moves to exactly 10.
484 /// assert_eq!(map.insert_before(10, 'z', ()), (10, Some(())));
485 /// assert_eq!(map.get_index_of(&'z'), Some(10));
486 /// assert_eq!(map.get_index_of(&'*'), Some(11));
487 ///
488 /// // Moving or inserting before the endpoint is also valid.
489 /// assert_eq!(map.len(), 27);
490 /// assert_eq!(map.insert_before(map.len(), '*', ()), (26, Some(())));
491 /// assert_eq!(map.get_index_of(&'*'), Some(26));
492 /// assert_eq!(map.insert_before(map.len(), '+', ()), (27, None));
493 /// assert_eq!(map.get_index_of(&'+'), Some(27));
494 /// assert_eq!(map.len(), 28);
495 /// ```
496 pub fn insert_before(&mut self, mut index: usize, key: K, value: V) -> (usize, Option<V>) {
497 assert!(index <= self.len(), "index out of bounds");
498 match self.entry(key) {
499 Entry::Occupied(mut entry) => {
500 if index > entry.index() {
501 // Some entries will shift down when this one moves up,
502 // so "insert before index" becomes "move to index - 1",
503 // keeping the entry at the original index unmoved.
504 index -= 1;
505 }
506 let old = mem::replace(entry.get_mut(), value);
507 entry.move_index(index);
508 (index, Some(old))
509 }
510 Entry::Vacant(entry) => {
511 entry.shift_insert(index, value);
512 (index, None)
513 }
514 }
515 }
516
517 /// Insert a key-value pair in the map at the given index.
518 ///
519 /// If an equivalent key already exists in the map: the key remains and
520 /// is moved to the given index in the map, its corresponding value is updated
521 /// with `value`, and the older value is returned inside `Some(_)`.
522 /// Note that existing entries **cannot** be moved to `index == map.len()`!
523 /// (See [`insert_before`](Self::insert_before) for different behavior here.)
524 ///
525 /// If no equivalent key existed in the map: the new key-value pair is
526 /// inserted at the given index, and `None` is returned.
527 ///
528 /// ***Panics*** if `index` is out of bounds.
529 /// Valid indices are `0..map.len()` (exclusive) when moving an existing entry, or
530 /// `0..=map.len()` (inclusive) when inserting a new key.
531 ///
532 /// Computes in **O(n)** time (average).
533 ///
534 /// See also [`entry`][Self::entry] if you want to insert *or* modify,
535 /// perhaps only using the index for new entries with [`VacantEntry::shift_insert`].
536 ///
537 /// # Examples
538 ///
539 /// ```
540 /// use indexmap::IndexMap;
541 /// let mut map: IndexMap<char, ()> = ('a'..='z').map(|c| (c, ())).collect();
542 ///
543 /// // The new key '*' goes exactly at the given index.
544 /// assert_eq!(map.get_index_of(&'*'), None);
545 /// assert_eq!(map.shift_insert(10, '*', ()), None);
546 /// assert_eq!(map.get_index_of(&'*'), Some(10));
547 ///
548 /// // Moving the key 'a' up to 10 will shift others down, including the '*' that was at 10.
549 /// assert_eq!(map.shift_insert(10, 'a', ()), Some(()));
550 /// assert_eq!(map.get_index_of(&'a'), Some(10));
551 /// assert_eq!(map.get_index_of(&'*'), Some(9));
552 ///
553 /// // Moving the key 'z' down to 9 will shift others up, including the '*' that was at 9.
554 /// assert_eq!(map.shift_insert(9, 'z', ()), Some(()));
555 /// assert_eq!(map.get_index_of(&'z'), Some(9));
556 /// assert_eq!(map.get_index_of(&'*'), Some(10));
557 ///
558 /// // Existing keys can move to len-1 at most, but new keys can insert at the endpoint.
559 /// assert_eq!(map.len(), 27);
560 /// assert_eq!(map.shift_insert(map.len() - 1, '*', ()), Some(()));
561 /// assert_eq!(map.get_index_of(&'*'), Some(26));
562 /// assert_eq!(map.shift_insert(map.len(), '+', ()), None);
563 /// assert_eq!(map.get_index_of(&'+'), Some(27));
564 /// assert_eq!(map.len(), 28);
565 /// ```
566 ///
567 /// ```should_panic
568 /// use indexmap::IndexMap;
569 /// let mut map: IndexMap<char, ()> = ('a'..='z').map(|c| (c, ())).collect();
570 ///
571 /// // This is an invalid index for moving an existing key!
572 /// map.shift_insert(map.len(), 'a', ());
573 /// ```
574 pub fn shift_insert(&mut self, index: usize, key: K, value: V) -> Option<V> {
575 let len = self.len();
576 match self.entry(key) {
577 Entry::Occupied(mut entry) => {
578 assert!(index < len, "index out of bounds");
579 let old = mem::replace(entry.get_mut(), value);
580 entry.move_index(index);
581 Some(old)
582 }
583 Entry::Vacant(entry) => {
584 assert!(index <= len, "index out of bounds");
585 entry.shift_insert(index, value);
586 None
587 }
588 }
589 }
590
591 /// Get the given key’s corresponding entry in the map for insertion and/or
592 /// in-place manipulation.
593 ///
594 /// Computes in **O(1)** time (amortized average).
595 pub fn entry(&mut self, key: K) -> Entry<'_, K, V> {
596 let hash = self.hash(&key);
597 self.core.entry(hash, key)
598 }
599
600 /// Creates a splicing iterator that replaces the specified range in the map
601 /// with the given `replace_with` key-value iterator and yields the removed
602 /// items. `replace_with` does not need to be the same length as `range`.
603 ///
604 /// The `range` is removed even if the iterator is not consumed until the
605 /// end. It is unspecified how many elements are removed from the map if the
606 /// `Splice` value is leaked.
607 ///
608 /// The input iterator `replace_with` is only consumed when the `Splice`
609 /// value is dropped. If a key from the iterator matches an existing entry
610 /// in the map (outside of `range`), then the value will be updated in that
611 /// position. Otherwise, the new key-value pair will be inserted in the
612 /// replaced `range`.
613 ///
614 /// ***Panics*** if the starting point is greater than the end point or if
615 /// the end point is greater than the length of the map.
616 ///
617 /// # Examples
618 ///
619 /// ```
620 /// use indexmap::IndexMap;
621 ///
622 /// let mut map = IndexMap::from([(0, '_'), (1, 'a'), (2, 'b'), (3, 'c'), (4, 'd')]);
623 /// let new = [(5, 'E'), (4, 'D'), (3, 'C'), (2, 'B'), (1, 'A')];
624 /// let removed: Vec<_> = map.splice(2..4, new).collect();
625 ///
626 /// // 1 and 4 got new values, while 5, 3, and 2 were newly inserted.
627 /// assert!(map.into_iter().eq([(0, '_'), (1, 'A'), (5, 'E'), (3, 'C'), (2, 'B'), (4, 'D')]));
628 /// assert_eq!(removed, &[(2, 'b'), (3, 'c')]);
629 /// ```
630 pub fn splice<R, I>(&mut self, range: R, replace_with: I) -> Splice<'_, I::IntoIter, K, V, S>
631 where
632 R: RangeBounds<usize>,
633 I: IntoIterator<Item = (K, V)>,
634 {
635 Splice::new(self, range, replace_with.into_iter())
636 }
637
638 /// Moves all key-value pairs from `other` into `self`, leaving `other` empty.
639 ///
640 /// This is equivalent to calling [`insert`][Self::insert] for each
641 /// key-value pair from `other` in order, which means that for keys that
642 /// already exist in `self`, their value is updated in the current position.
643 ///
644 /// # Examples
645 ///
646 /// ```
647 /// use indexmap::IndexMap;
648 ///
649 /// // Note: Key (3) is present in both maps.
650 /// let mut a = IndexMap::from([(3, "c"), (2, "b"), (1, "a")]);
651 /// let mut b = IndexMap::from([(3, "d"), (4, "e"), (5, "f")]);
652 /// let old_capacity = b.capacity();
653 ///
654 /// a.append(&mut b);
655 ///
656 /// assert_eq!(a.len(), 5);
657 /// assert_eq!(b.len(), 0);
658 /// assert_eq!(b.capacity(), old_capacity);
659 ///
660 /// assert!(a.keys().eq(&[3, 2, 1, 4, 5]));
661 /// assert_eq!(a[&3], "d"); // "c" was overwritten.
662 /// ```
663 pub fn append<S2>(&mut self, other: &mut IndexMap<K, V, S2>) {
664 self.extend(other.drain(..));
665 }
666}
667
668impl<K, V, S> IndexMap<K, V, S>
669where
670 S: BuildHasher,
671{
672 pub(crate) fn hash<Q: ?Sized + Hash>(&self, key: &Q) -> HashValue {
673 let mut h = self.hash_builder.build_hasher();
674 key.hash(&mut h);
675 HashValue(h.finish() as usize)
676 }
677
678 /// Return `true` if an equivalent to `key` exists in the map.
679 ///
680 /// Computes in **O(1)** time (average).
681 pub fn contains_key<Q>(&self, key: &Q) -> bool
682 where
683 Q: ?Sized + Hash + Equivalent<K>,
684 {
685 self.get_index_of(key).is_some()
686 }
687
688 /// Return a reference to the value stored for `key`, if it is present,
689 /// else `None`.
690 ///
691 /// Computes in **O(1)** time (average).
692 pub fn get<Q>(&self, key: &Q) -> Option<&V>
693 where
694 Q: ?Sized + Hash + Equivalent<K>,
695 {
696 if let Some(i) = self.get_index_of(key) {
697 let entry = &self.as_entries()[i];
698 Some(&entry.value)
699 } else {
700 None
701 }
702 }
703
704 /// Return references to the key-value pair stored for `key`,
705 /// if it is present, else `None`.
706 ///
707 /// Computes in **O(1)** time (average).
708 pub fn get_key_value<Q>(&self, key: &Q) -> Option<(&K, &V)>
709 where
710 Q: ?Sized + Hash + Equivalent<K>,
711 {
712 if let Some(i) = self.get_index_of(key) {
713 let entry = &self.as_entries()[i];
714 Some((&entry.key, &entry.value))
715 } else {
716 None
717 }
718 }
719
720 /// Return item index, key and value
721 pub fn get_full<Q>(&self, key: &Q) -> Option<(usize, &K, &V)>
722 where
723 Q: ?Sized + Hash + Equivalent<K>,
724 {
725 if let Some(i) = self.get_index_of(key) {
726 let entry = &self.as_entries()[i];
727 Some((i, &entry.key, &entry.value))
728 } else {
729 None
730 }
731 }
732
733 /// Return item index, if it exists in the map
734 ///
735 /// Computes in **O(1)** time (average).
736 pub fn get_index_of<Q>(&self, key: &Q) -> Option<usize>
737 where
738 Q: ?Sized + Hash + Equivalent<K>,
739 {
740 match self.as_entries() {
741 [] => None,
742 [x] => key.equivalent(&x.key).then_some(0),
743 _ => {
744 let hash = self.hash(key);
745 self.core.get_index_of(hash, key)
746 }
747 }
748 }
749
750 pub fn get_mut<Q>(&mut self, key: &Q) -> Option<&mut V>
751 where
752 Q: ?Sized + Hash + Equivalent<K>,
753 {
754 if let Some(i) = self.get_index_of(key) {
755 let entry = &mut self.as_entries_mut()[i];
756 Some(&mut entry.value)
757 } else {
758 None
759 }
760 }
761
762 pub fn get_full_mut<Q>(&mut self, key: &Q) -> Option<(usize, &K, &mut V)>
763 where
764 Q: ?Sized + Hash + Equivalent<K>,
765 {
766 if let Some(i) = self.get_index_of(key) {
767 let entry = &mut self.as_entries_mut()[i];
768 Some((i, &entry.key, &mut entry.value))
769 } else {
770 None
771 }
772 }
773
774 /// Remove the key-value pair equivalent to `key` and return
775 /// its value.
776 ///
777 /// **NOTE:** This is equivalent to [`.swap_remove(key)`][Self::swap_remove], replacing this
778 /// entry's position with the last element, and it is deprecated in favor of calling that
779 /// explicitly. If you need to preserve the relative order of the keys in the map, use
780 /// [`.shift_remove(key)`][Self::shift_remove] instead.
781 #[deprecated(note = "`remove` disrupts the map order -- \
782 use `swap_remove` or `shift_remove` for explicit behavior.")]
783 pub fn remove<Q>(&mut self, key: &Q) -> Option<V>
784 where
785 Q: ?Sized + Hash + Equivalent<K>,
786 {
787 self.swap_remove(key)
788 }
789
790 /// Remove and return the key-value pair equivalent to `key`.
791 ///
792 /// **NOTE:** This is equivalent to [`.swap_remove_entry(key)`][Self::swap_remove_entry],
793 /// replacing this entry's position with the last element, and it is deprecated in favor of
794 /// calling that explicitly. If you need to preserve the relative order of the keys in the map,
795 /// use [`.shift_remove_entry(key)`][Self::shift_remove_entry] instead.
796 #[deprecated(note = "`remove_entry` disrupts the map order -- \
797 use `swap_remove_entry` or `shift_remove_entry` for explicit behavior.")]
798 pub fn remove_entry<Q>(&mut self, key: &Q) -> Option<(K, V)>
799 where
800 Q: ?Sized + Hash + Equivalent<K>,
801 {
802 self.swap_remove_entry(key)
803 }
804
805 /// Remove the key-value pair equivalent to `key` and return
806 /// its value.
807 ///
808 /// Like [`Vec::swap_remove`], the pair is removed by swapping it with the
809 /// last element of the map and popping it off. **This perturbs
810 /// the position of what used to be the last element!**
811 ///
812 /// Return `None` if `key` is not in map.
813 ///
814 /// Computes in **O(1)** time (average).
815 pub fn swap_remove<Q>(&mut self, key: &Q) -> Option<V>
816 where
817 Q: ?Sized + Hash + Equivalent<K>,
818 {
819 self.swap_remove_full(key).map(third)
820 }
821
822 /// Remove and return the key-value pair equivalent to `key`.
823 ///
824 /// Like [`Vec::swap_remove`], the pair is removed by swapping it with the
825 /// last element of the map and popping it off. **This perturbs
826 /// the position of what used to be the last element!**
827 ///
828 /// Return `None` if `key` is not in map.
829 ///
830 /// Computes in **O(1)** time (average).
831 pub fn swap_remove_entry<Q>(&mut self, key: &Q) -> Option<(K, V)>
832 where
833 Q: ?Sized + Hash + Equivalent<K>,
834 {
835 match self.swap_remove_full(key) {
836 Some((_, key, value)) => Some((key, value)),
837 None => None,
838 }
839 }
840
841 /// Remove the key-value pair equivalent to `key` and return it and
842 /// the index it had.
843 ///
844 /// Like [`Vec::swap_remove`], the pair is removed by swapping it with the
845 /// last element of the map and popping it off. **This perturbs
846 /// the position of what used to be the last element!**
847 ///
848 /// Return `None` if `key` is not in map.
849 ///
850 /// Computes in **O(1)** time (average).
851 pub fn swap_remove_full<Q>(&mut self, key: &Q) -> Option<(usize, K, V)>
852 where
853 Q: ?Sized + Hash + Equivalent<K>,
854 {
855 match self.as_entries() {
856 [x] if key.equivalent(&x.key) => {
857 let (k, v) = self.core.pop()?;
858 Some((0, k, v))
859 }
860 [_] | [] => None,
861 _ => {
862 let hash = self.hash(key);
863 self.core.swap_remove_full(hash, key)
864 }
865 }
866 }
867
868 /// Remove the key-value pair equivalent to `key` and return
869 /// its value.
870 ///
871 /// Like [`Vec::remove`], the pair is removed by shifting all of the
872 /// elements that follow it, preserving their relative order.
873 /// **This perturbs the index of all of those elements!**
874 ///
875 /// Return `None` if `key` is not in map.
876 ///
877 /// Computes in **O(n)** time (average).
878 pub fn shift_remove<Q>(&mut self, key: &Q) -> Option<V>
879 where
880 Q: ?Sized + Hash + Equivalent<K>,
881 {
882 self.shift_remove_full(key).map(third)
883 }
884
885 /// Remove and return the key-value pair equivalent to `key`.
886 ///
887 /// Like [`Vec::remove`], the pair is removed by shifting all of the
888 /// elements that follow it, preserving their relative order.
889 /// **This perturbs the index of all of those elements!**
890 ///
891 /// Return `None` if `key` is not in map.
892 ///
893 /// Computes in **O(n)** time (average).
894 pub fn shift_remove_entry<Q>(&mut self, key: &Q) -> Option<(K, V)>
895 where
896 Q: ?Sized + Hash + Equivalent<K>,
897 {
898 match self.shift_remove_full(key) {
899 Some((_, key, value)) => Some((key, value)),
900 None => None,
901 }
902 }
903
904 /// Remove the key-value pair equivalent to `key` and return it and
905 /// the index it had.
906 ///
907 /// Like [`Vec::remove`], the pair is removed by shifting all of the
908 /// elements that follow it, preserving their relative order.
909 /// **This perturbs the index of all of those elements!**
910 ///
911 /// Return `None` if `key` is not in map.
912 ///
913 /// Computes in **O(n)** time (average).
914 pub fn shift_remove_full<Q>(&mut self, key: &Q) -> Option<(usize, K, V)>
915 where
916 Q: ?Sized + Hash + Equivalent<K>,
917 {
918 match self.as_entries() {
919 [x] if key.equivalent(&x.key) => {
920 let (k, v) = self.core.pop()?;
921 Some((0, k, v))
922 }
923 [_] | [] => None,
924 _ => {
925 let hash = self.hash(key);
926 self.core.shift_remove_full(hash, key)
927 }
928 }
929 }
930}
931
932impl<K, V, S> IndexMap<K, V, S> {
933 /// Remove the last key-value pair
934 ///
935 /// This preserves the order of the remaining elements.
936 ///
937 /// Computes in **O(1)** time (average).
938 #[doc(alias = "pop_last")] // like `BTreeMap`
939 pub fn pop(&mut self) -> Option<(K, V)> {
940 self.core.pop()
941 }
942
943 /// Scan through each key-value pair in the map and keep those where the
944 /// closure `keep` returns `true`.
945 ///
946 /// The elements are visited in order, and remaining elements keep their
947 /// order.
948 ///
949 /// Computes in **O(n)** time (average).
950 pub fn retain<F>(&mut self, mut keep: F)
951 where
952 F: FnMut(&K, &mut V) -> bool,
953 {
954 self.core.retain_in_order(move |k, v| keep(k, v));
955 }
956
957 /// Sort the map’s key-value pairs by the default ordering of the keys.
958 ///
959 /// This is a stable sort -- but equivalent keys should not normally coexist in
960 /// a map at all, so [`sort_unstable_keys`][Self::sort_unstable_keys] is preferred
961 /// because it is generally faster and doesn't allocate auxiliary memory.
962 ///
963 /// See [`sort_by`](Self::sort_by) for details.
964 pub fn sort_keys(&mut self)
965 where
966 K: Ord,
967 {
968 self.with_entries(move |entries| {
969 entries.sort_by(move |a, b| K::cmp(&a.key, &b.key));
970 });
971 }
972
973 /// Sort the map’s key-value pairs in place using the comparison
974 /// function `cmp`.
975 ///
976 /// The comparison function receives two key and value pairs to compare (you
977 /// can sort by keys or values or their combination as needed).
978 ///
979 /// Computes in **O(n log n + c)** time and **O(n)** space where *n* is
980 /// the length of the map and *c* the capacity. The sort is stable.
981 pub fn sort_by<F>(&mut self, mut cmp: F)
982 where
983 F: FnMut(&K, &V, &K, &V) -> Ordering,
984 {
985 self.with_entries(move |entries| {
986 entries.sort_by(move |a, b| cmp(&a.key, &a.value, &b.key, &b.value));
987 });
988 }
989
990 /// Sort the key-value pairs of the map and return a by-value iterator of
991 /// the key-value pairs with the result.
992 ///
993 /// The sort is stable.
994 pub fn sorted_by<F>(self, mut cmp: F) -> IntoIter<K, V>
995 where
996 F: FnMut(&K, &V, &K, &V) -> Ordering,
997 {
998 let mut entries = self.into_entries();
999 entries.sort_by(move |a, b| cmp(&a.key, &a.value, &b.key, &b.value));
1000 IntoIter::new(entries)
1001 }
1002
1003 /// Sort the map's key-value pairs by the default ordering of the keys, but
1004 /// may not preserve the order of equal elements.
1005 ///
1006 /// See [`sort_unstable_by`](Self::sort_unstable_by) for details.
1007 pub fn sort_unstable_keys(&mut self)
1008 where
1009 K: Ord,
1010 {
1011 self.with_entries(move |entries| {
1012 entries.sort_unstable_by(move |a, b| K::cmp(&a.key, &b.key));
1013 });
1014 }
1015
1016 /// Sort the map's key-value pairs in place using the comparison function `cmp`, but
1017 /// may not preserve the order of equal elements.
1018 ///
1019 /// The comparison function receives two key and value pairs to compare (you
1020 /// can sort by keys or values or their combination as needed).
1021 ///
1022 /// Computes in **O(n log n + c)** time where *n* is
1023 /// the length of the map and *c* is the capacity. The sort is unstable.
1024 pub fn sort_unstable_by<F>(&mut self, mut cmp: F)
1025 where
1026 F: FnMut(&K, &V, &K, &V) -> Ordering,
1027 {
1028 self.with_entries(move |entries| {
1029 entries.sort_unstable_by(move |a, b| cmp(&a.key, &a.value, &b.key, &b.value));
1030 });
1031 }
1032
1033 /// Sort the key-value pairs of the map and return a by-value iterator of
1034 /// the key-value pairs with the result.
1035 ///
1036 /// The sort is unstable.
1037 #[inline]
1038 pub fn sorted_unstable_by<F>(self, mut cmp: F) -> IntoIter<K, V>
1039 where
1040 F: FnMut(&K, &V, &K, &V) -> Ordering,
1041 {
1042 let mut entries = self.into_entries();
1043 entries.sort_unstable_by(move |a, b| cmp(&a.key, &a.value, &b.key, &b.value));
1044 IntoIter::new(entries)
1045 }
1046
1047 /// Sort the map’s key-value pairs in place using a sort-key extraction function.
1048 ///
1049 /// During sorting, the function is called at most once per entry, by using temporary storage
1050 /// to remember the results of its evaluation. The order of calls to the function is
1051 /// unspecified and may change between versions of `indexmap` or the standard library.
1052 ///
1053 /// Computes in **O(m n + n log n + c)** time () and **O(n)** space, where the function is
1054 /// **O(m)**, *n* is the length of the map, and *c* the capacity. The sort is stable.
1055 pub fn sort_by_cached_key<T, F>(&mut self, mut sort_key: F)
1056 where
1057 T: Ord,
1058 F: FnMut(&K, &V) -> T,
1059 {
1060 self.with_entries(move |entries| {
1061 entries.sort_by_cached_key(move |a| sort_key(&a.key, &a.value));
1062 });
1063 }
1064
1065 /// Search over a sorted map for a key.
1066 ///
1067 /// Returns the position where that key is present, or the position where it can be inserted to
1068 /// maintain the sort. See [`slice::binary_search`] for more details.
1069 ///
1070 /// Computes in **O(log(n))** time, which is notably less scalable than looking the key up
1071 /// using [`get_index_of`][IndexMap::get_index_of], but this can also position missing keys.
1072 pub fn binary_search_keys(&self, x: &K) -> Result<usize, usize>
1073 where
1074 K: Ord,
1075 {
1076 self.as_slice().binary_search_keys(x)
1077 }
1078
1079 /// Search over a sorted map with a comparator function.
1080 ///
1081 /// Returns the position where that value is present, or the position where it can be inserted
1082 /// to maintain the sort. See [`slice::binary_search_by`] for more details.
1083 ///
1084 /// Computes in **O(log(n))** time.
1085 #[inline]
1086 pub fn binary_search_by<'a, F>(&'a self, f: F) -> Result<usize, usize>
1087 where
1088 F: FnMut(&'a K, &'a V) -> Ordering,
1089 {
1090 self.as_slice().binary_search_by(f)
1091 }
1092
1093 /// Search over a sorted map with an extraction function.
1094 ///
1095 /// Returns the position where that value is present, or the position where it can be inserted
1096 /// to maintain the sort. See [`slice::binary_search_by_key`] for more details.
1097 ///
1098 /// Computes in **O(log(n))** time.
1099 #[inline]
1100 pub fn binary_search_by_key<'a, B, F>(&'a self, b: &B, f: F) -> Result<usize, usize>
1101 where
1102 F: FnMut(&'a K, &'a V) -> B,
1103 B: Ord,
1104 {
1105 self.as_slice().binary_search_by_key(b, f)
1106 }
1107
1108 /// Returns the index of the partition point of a sorted map according to the given predicate
1109 /// (the index of the first element of the second partition).
1110 ///
1111 /// See [`slice::partition_point`] for more details.
1112 ///
1113 /// Computes in **O(log(n))** time.
1114 #[must_use]
1115 pub fn partition_point<P>(&self, pred: P) -> usize
1116 where
1117 P: FnMut(&K, &V) -> bool,
1118 {
1119 self.as_slice().partition_point(pred)
1120 }
1121
1122 /// Reverses the order of the map’s key-value pairs in place.
1123 ///
1124 /// Computes in **O(n)** time and **O(1)** space.
1125 pub fn reverse(&mut self) {
1126 self.core.reverse()
1127 }
1128
1129 /// Returns a slice of all the key-value pairs in the map.
1130 ///
1131 /// Computes in **O(1)** time.
1132 pub fn as_slice(&self) -> &Slice<K, V> {
1133 Slice::from_slice(self.as_entries())
1134 }
1135
1136 /// Returns a mutable slice of all the key-value pairs in the map.
1137 ///
1138 /// Computes in **O(1)** time.
1139 pub fn as_mut_slice(&mut self) -> &mut Slice<K, V> {
1140 Slice::from_mut_slice(self.as_entries_mut())
1141 }
1142
1143 /// Converts into a boxed slice of all the key-value pairs in the map.
1144 ///
1145 /// Note that this will drop the inner hash table and any excess capacity.
1146 pub fn into_boxed_slice(self) -> Box<Slice<K, V>> {
1147 Slice::from_boxed(self.into_entries().into_boxed_slice())
1148 }
1149
1150 /// Get a key-value pair by index
1151 ///
1152 /// Valid indices are `0 <= index < self.len()`.
1153 ///
1154 /// Computes in **O(1)** time.
1155 pub fn get_index(&self, index: usize) -> Option<(&K, &V)> {
1156 self.as_entries().get(index).map(Bucket::refs)
1157 }
1158
1159 /// Get a key-value pair by index
1160 ///
1161 /// Valid indices are `0 <= index < self.len()`.
1162 ///
1163 /// Computes in **O(1)** time.
1164 pub fn get_index_mut(&mut self, index: usize) -> Option<(&K, &mut V)> {
1165 self.as_entries_mut().get_mut(index).map(Bucket::ref_mut)
1166 }
1167
1168 /// Get an entry in the map by index for in-place manipulation.
1169 ///
1170 /// Valid indices are `0 <= index < self.len()`.
1171 ///
1172 /// Computes in **O(1)** time.
1173 pub fn get_index_entry(&mut self, index: usize) -> Option<IndexedEntry<'_, K, V>> {
1174 if index >= self.len() {
1175 return None;
1176 }
1177 Some(IndexedEntry::new(&mut self.core, index))
1178 }
1179
1180 /// Returns a slice of key-value pairs in the given range of indices.
1181 ///
1182 /// Valid indices are `0 <= index < self.len()`.
1183 ///
1184 /// Computes in **O(1)** time.
1185 pub fn get_range<R: RangeBounds<usize>>(&self, range: R) -> Option<&Slice<K, V>> {
1186 let entries = self.as_entries();
1187 let range = try_simplify_range(range, entries.len())?;
1188 entries.get(range).map(Slice::from_slice)
1189 }
1190
1191 /// Returns a mutable slice of key-value pairs in the given range of indices.
1192 ///
1193 /// Valid indices are `0 <= index < self.len()`.
1194 ///
1195 /// Computes in **O(1)** time.
1196 pub fn get_range_mut<R: RangeBounds<usize>>(&mut self, range: R) -> Option<&mut Slice<K, V>> {
1197 let entries = self.as_entries_mut();
1198 let range = try_simplify_range(range, entries.len())?;
1199 entries.get_mut(range).map(Slice::from_mut_slice)
1200 }
1201
1202 /// Get the first key-value pair
1203 ///
1204 /// Computes in **O(1)** time.
1205 #[doc(alias = "first_key_value")] // like `BTreeMap`
1206 pub fn first(&self) -> Option<(&K, &V)> {
1207 self.as_entries().first().map(Bucket::refs)
1208 }
1209
1210 /// Get the first key-value pair, with mutable access to the value
1211 ///
1212 /// Computes in **O(1)** time.
1213 pub fn first_mut(&mut self) -> Option<(&K, &mut V)> {
1214 self.as_entries_mut().first_mut().map(Bucket::ref_mut)
1215 }
1216
1217 /// Get the first entry in the map for in-place manipulation.
1218 ///
1219 /// Computes in **O(1)** time.
1220 pub fn first_entry(&mut self) -> Option<IndexedEntry<'_, K, V>> {
1221 self.get_index_entry(0)
1222 }
1223
1224 /// Get the last key-value pair
1225 ///
1226 /// Computes in **O(1)** time.
1227 #[doc(alias = "last_key_value")] // like `BTreeMap`
1228 pub fn last(&self) -> Option<(&K, &V)> {
1229 self.as_entries().last().map(Bucket::refs)
1230 }
1231
1232 /// Get the last key-value pair, with mutable access to the value
1233 ///
1234 /// Computes in **O(1)** time.
1235 pub fn last_mut(&mut self) -> Option<(&K, &mut V)> {
1236 self.as_entries_mut().last_mut().map(Bucket::ref_mut)
1237 }
1238
1239 /// Get the last entry in the map for in-place manipulation.
1240 ///
1241 /// Computes in **O(1)** time.
1242 pub fn last_entry(&mut self) -> Option<IndexedEntry<'_, K, V>> {
1243 self.get_index_entry(self.len().checked_sub(1)?)
1244 }
1245
1246 /// Remove the key-value pair by index
1247 ///
1248 /// Valid indices are `0 <= index < self.len()`.
1249 ///
1250 /// Like [`Vec::swap_remove`], the pair is removed by swapping it with the
1251 /// last element of the map and popping it off. **This perturbs
1252 /// the position of what used to be the last element!**
1253 ///
1254 /// Computes in **O(1)** time (average).
1255 pub fn swap_remove_index(&mut self, index: usize) -> Option<(K, V)> {
1256 self.core.swap_remove_index(index)
1257 }
1258
1259 /// Remove the key-value pair by index
1260 ///
1261 /// Valid indices are `0 <= index < self.len()`.
1262 ///
1263 /// Like [`Vec::remove`], the pair is removed by shifting all of the
1264 /// elements that follow it, preserving their relative order.
1265 /// **This perturbs the index of all of those elements!**
1266 ///
1267 /// Computes in **O(n)** time (average).
1268 pub fn shift_remove_index(&mut self, index: usize) -> Option<(K, V)> {
1269 self.core.shift_remove_index(index)
1270 }
1271
1272 /// Moves the position of a key-value pair from one index to another
1273 /// by shifting all other pairs in-between.
1274 ///
1275 /// * If `from < to`, the other pairs will shift down while the targeted pair moves up.
1276 /// * If `from > to`, the other pairs will shift up while the targeted pair moves down.
1277 ///
1278 /// ***Panics*** if `from` or `to` are out of bounds.
1279 ///
1280 /// Computes in **O(n)** time (average).
1281 pub fn move_index(&mut self, from: usize, to: usize) {
1282 self.core.move_index(from, to)
1283 }
1284
1285 /// Swaps the position of two key-value pairs in the map.
1286 ///
1287 /// ***Panics*** if `a` or `b` are out of bounds.
1288 ///
1289 /// Computes in **O(1)** time (average).
1290 pub fn swap_indices(&mut self, a: usize, b: usize) {
1291 self.core.swap_indices(a, b)
1292 }
1293}
1294
1295/// Access [`IndexMap`] values corresponding to a key.
1296///
1297/// # Examples
1298///
1299/// ```
1300/// use indexmap::IndexMap;
1301///
1302/// let mut map = IndexMap::new();
1303/// for word in "Lorem ipsum dolor sit amet".split_whitespace() {
1304/// map.insert(word.to_lowercase(), word.to_uppercase());
1305/// }
1306/// assert_eq!(map["lorem"], "LOREM");
1307/// assert_eq!(map["ipsum"], "IPSUM");
1308/// ```
1309///
1310/// ```should_panic
1311/// use indexmap::IndexMap;
1312///
1313/// let mut map = IndexMap::new();
1314/// map.insert("foo", 1);
1315/// println!("{:?}", map["bar"]); // panics!
1316/// ```
1317impl<K, V, Q: ?Sized, S> Index<&Q> for IndexMap<K, V, S>
1318where
1319 Q: Hash + Equivalent<K>,
1320 S: BuildHasher,
1321{
1322 type Output = V;
1323
1324 /// Returns a reference to the value corresponding to the supplied `key`.
1325 ///
1326 /// ***Panics*** if `key` is not present in the map.
1327 fn index(&self, key: &Q) -> &V {
1328 self.get(key).expect(msg:"IndexMap: key not found")
1329 }
1330}
1331
1332/// Access [`IndexMap`] values corresponding to a key.
1333///
1334/// Mutable indexing allows changing / updating values of key-value
1335/// pairs that are already present.
1336///
1337/// You can **not** insert new pairs with index syntax, use `.insert()`.
1338///
1339/// # Examples
1340///
1341/// ```
1342/// use indexmap::IndexMap;
1343///
1344/// let mut map = IndexMap::new();
1345/// for word in "Lorem ipsum dolor sit amet".split_whitespace() {
1346/// map.insert(word.to_lowercase(), word.to_string());
1347/// }
1348/// let lorem = &mut map["lorem"];
1349/// assert_eq!(lorem, "Lorem");
1350/// lorem.retain(char::is_lowercase);
1351/// assert_eq!(map["lorem"], "orem");
1352/// ```
1353///
1354/// ```should_panic
1355/// use indexmap::IndexMap;
1356///
1357/// let mut map = IndexMap::new();
1358/// map.insert("foo", 1);
1359/// map["bar"] = 1; // panics!
1360/// ```
1361impl<K, V, Q: ?Sized, S> IndexMut<&Q> for IndexMap<K, V, S>
1362where
1363 Q: Hash + Equivalent<K>,
1364 S: BuildHasher,
1365{
1366 /// Returns a mutable reference to the value corresponding to the supplied `key`.
1367 ///
1368 /// ***Panics*** if `key` is not present in the map.
1369 fn index_mut(&mut self, key: &Q) -> &mut V {
1370 self.get_mut(key).expect(msg:"IndexMap: key not found")
1371 }
1372}
1373
1374/// Access [`IndexMap`] values at indexed positions.
1375///
1376/// See [`Index<usize> for Keys`][keys] to access a map's keys instead.
1377///
1378/// [keys]: Keys#impl-Index<usize>-for-Keys<'a,+K,+V>
1379///
1380/// # Examples
1381///
1382/// ```
1383/// use indexmap::IndexMap;
1384///
1385/// let mut map = IndexMap::new();
1386/// for word in "Lorem ipsum dolor sit amet".split_whitespace() {
1387/// map.insert(word.to_lowercase(), word.to_uppercase());
1388/// }
1389/// assert_eq!(map[0], "LOREM");
1390/// assert_eq!(map[1], "IPSUM");
1391/// map.reverse();
1392/// assert_eq!(map[0], "AMET");
1393/// assert_eq!(map[1], "SIT");
1394/// map.sort_keys();
1395/// assert_eq!(map[0], "AMET");
1396/// assert_eq!(map[1], "DOLOR");
1397/// ```
1398///
1399/// ```should_panic
1400/// use indexmap::IndexMap;
1401///
1402/// let mut map = IndexMap::new();
1403/// map.insert("foo", 1);
1404/// println!("{:?}", map[10]); // panics!
1405/// ```
1406impl<K, V, S> Index<usize> for IndexMap<K, V, S> {
1407 type Output = V;
1408
1409 /// Returns a reference to the value at the supplied `index`.
1410 ///
1411 /// ***Panics*** if `index` is out of bounds.
1412 fn index(&self, index: usize) -> &V {
1413 self.get_index(index)
1414 .expect(msg:"IndexMap: index out of bounds")
1415 .1
1416 }
1417}
1418
1419/// Access [`IndexMap`] values at indexed positions.
1420///
1421/// Mutable indexing allows changing / updating indexed values
1422/// that are already present.
1423///
1424/// You can **not** insert new values with index syntax -- use [`.insert()`][IndexMap::insert].
1425///
1426/// # Examples
1427///
1428/// ```
1429/// use indexmap::IndexMap;
1430///
1431/// let mut map = IndexMap::new();
1432/// for word in "Lorem ipsum dolor sit amet".split_whitespace() {
1433/// map.insert(word.to_lowercase(), word.to_string());
1434/// }
1435/// let lorem = &mut map[0];
1436/// assert_eq!(lorem, "Lorem");
1437/// lorem.retain(char::is_lowercase);
1438/// assert_eq!(map["lorem"], "orem");
1439/// ```
1440///
1441/// ```should_panic
1442/// use indexmap::IndexMap;
1443///
1444/// let mut map = IndexMap::new();
1445/// map.insert("foo", 1);
1446/// map[10] = 1; // panics!
1447/// ```
1448impl<K, V, S> IndexMut<usize> for IndexMap<K, V, S> {
1449 /// Returns a mutable reference to the value at the supplied `index`.
1450 ///
1451 /// ***Panics*** if `index` is out of bounds.
1452 fn index_mut(&mut self, index: usize) -> &mut V {
1453 self.get_index_mut(index)
1454 .expect(msg:"IndexMap: index out of bounds")
1455 .1
1456 }
1457}
1458
1459impl<K, V, S> FromIterator<(K, V)> for IndexMap<K, V, S>
1460where
1461 K: Hash + Eq,
1462 S: BuildHasher + Default,
1463{
1464 /// Create an `IndexMap` from the sequence of key-value pairs in the
1465 /// iterable.
1466 ///
1467 /// `from_iter` uses the same logic as `extend`. See
1468 /// [`extend`][IndexMap::extend] for more details.
1469 fn from_iter<I: IntoIterator<Item = (K, V)>>(iterable: I) -> Self {
1470 let iter: ::IntoIter = iterable.into_iter();
1471 let (low: usize, _) = iter.size_hint();
1472 let mut map: IndexMap = Self::with_capacity_and_hasher(n:low, <_>::default());
1473 map.extend(iter);
1474 map
1475 }
1476}
1477
1478#[cfg(feature = "std")]
1479#[cfg_attr(docsrs, doc(cfg(feature = "std")))]
1480impl<K, V, const N: usize> From<[(K, V); N]> for IndexMap<K, V, RandomState>
1481where
1482 K: Hash + Eq,
1483{
1484 /// # Examples
1485 ///
1486 /// ```
1487 /// use indexmap::IndexMap;
1488 ///
1489 /// let map1 = IndexMap::from([(1, 2), (3, 4)]);
1490 /// let map2: IndexMap<_, _> = [(1, 2), (3, 4)].into();
1491 /// assert_eq!(map1, map2);
1492 /// ```
1493 fn from(arr: [(K, V); N]) -> Self {
1494 Self::from_iter(arr)
1495 }
1496}
1497
1498impl<K, V, S> Extend<(K, V)> for IndexMap<K, V, S>
1499where
1500 K: Hash + Eq,
1501 S: BuildHasher,
1502{
1503 /// Extend the map with all key-value pairs in the iterable.
1504 ///
1505 /// This is equivalent to calling [`insert`][IndexMap::insert] for each of
1506 /// them in order, which means that for keys that already existed
1507 /// in the map, their value is updated but it keeps the existing order.
1508 ///
1509 /// New keys are inserted in the order they appear in the sequence. If
1510 /// equivalents of a key occur more than once, the last corresponding value
1511 /// prevails.
1512 fn extend<I: IntoIterator<Item = (K, V)>>(&mut self, iterable: I) {
1513 // (Note: this is a copy of `std`/`hashbrown`'s reservation logic.)
1514 // Keys may be already present or show multiple times in the iterator.
1515 // Reserve the entire hint lower bound if the map is empty.
1516 // Otherwise reserve half the hint (rounded up), so the map
1517 // will only resize twice in the worst case.
1518 let iter = iterable.into_iter();
1519 let reserve = if self.is_empty() {
1520 iter.size_hint().0
1521 } else {
1522 (iter.size_hint().0 + 1) / 2
1523 };
1524 self.reserve(reserve);
1525 iter.for_each(move |(k, v)| {
1526 self.insert(k, v);
1527 });
1528 }
1529}
1530
1531impl<'a, K, V, S> Extend<(&'a K, &'a V)> for IndexMap<K, V, S>
1532where
1533 K: Hash + Eq + Copy,
1534 V: Copy,
1535 S: BuildHasher,
1536{
1537 /// Extend the map with all key-value pairs in the iterable.
1538 ///
1539 /// See the first extend method for more details.
1540 fn extend<I: IntoIterator<Item = (&'a K, &'a V)>>(&mut self, iterable: I) {
1541 self.extend(iter:iterable.into_iter().map(|(&key: K, &value: V)| (key, value)));
1542 }
1543}
1544
1545impl<K, V, S> Default for IndexMap<K, V, S>
1546where
1547 S: Default,
1548{
1549 /// Return an empty [`IndexMap`]
1550 fn default() -> Self {
1551 Self::with_capacity_and_hasher(n:0, S::default())
1552 }
1553}
1554
1555impl<K, V1, S1, V2, S2> PartialEq<IndexMap<K, V2, S2>> for IndexMap<K, V1, S1>
1556where
1557 K: Hash + Eq,
1558 V1: PartialEq<V2>,
1559 S1: BuildHasher,
1560 S2: BuildHasher,
1561{
1562 fn eq(&self, other: &IndexMap<K, V2, S2>) -> bool {
1563 if self.len() != other.len() {
1564 return false;
1565 }
1566
1567 self.iter()
1568 .all(|(key: &K, value: &V1)| other.get(key).map_or(default:false, |v: &V2| *value == *v))
1569 }
1570}
1571
1572impl<K, V, S> Eq for IndexMap<K, V, S>
1573where
1574 K: Eq + Hash,
1575 V: Eq,
1576 S: BuildHasher,
1577{
1578}
1579