Struct indexmap::map::IndexMap [−][src]
pub struct IndexMap<K, V, S = RandomState> { /* fields omitted */ }
Expand description
A hash table where the iteration order of the key-value pairs is independent of the hash values of the keys.
The interface is closely compatible with the standard HashMap
, but also
has additional features.
Order
The key-value pairs have a consistent order that is determined by the sequence of insertion and removal calls on the map. The order does not depend on the keys or the hash function at all.
All iterators traverse the map in the order.
The insertion order is preserved, with notable exceptions like the
.remove()
or .swap_remove()
methods. Methods such as .sort_by()
of
course result in a new order, depending on the sorting order.
Indices
The key-value pairs are indexed in a compact range without holes in the
range 0..self.len()
. For example, the method .get_full
looks up the
index for a key, and the method .get_index
looks up the key-value pair by
index.
Examples
use indexmap::IndexMap;
// count the frequency of each letter in a sentence.
let mut letters = IndexMap::new();
for ch in "a short treatise on fungi".chars() {
*letters.entry(ch).or_insert(0) += 1;
}
assert_eq!(letters[&'s'], 2);
assert_eq!(letters[&'t'], 3);
assert_eq!(letters[&'u'], 1);
assert_eq!(letters.get(&'y'), None);
Implementations
Create a new map with capacity for n
key-value pairs. (Does not
allocate if n
is zero.)
Computes in O(n) time.
Create a new map with capacity for n
key-value pairs. (Does not
allocate if n
is zero.)
Computes in O(n) time.
Create a new map with hash_builder
.
This function is const
, so it
can be called in static
contexts.
Return the number of key-value pairs in the map.
Computes in O(1) time.
Returns true if the map contains no elements.
Computes in O(1) time.
Return an iterator over the key-value pairs of the map, in their order
Return an iterator over the key-value pairs of the map, in their order
Return an iterator over the keys of the map, in their order
Return an owning iterator over the keys of the map, in their order
Return an iterator over the values of the map, in their order
Return an iterator over mutable references to the values of the map, in their order
pub fn into_values(self) -> IntoValues<K, V>ⓘNotable traits for IntoValues<K, V>impl<K, V> Iterator for IntoValues<K, V> type Item = V;
pub fn into_values(self) -> IntoValues<K, V>ⓘNotable traits for IntoValues<K, V>impl<K, V> Iterator for IntoValues<K, V> type Item = V;
impl<K, V> Iterator for IntoValues<K, V> type Item = V;
Return an owning iterator over the values of the map, in their order
Remove all key-value pairs in the map, while preserving its capacity.
Computes in O(n) time.
Shortens the map, keeping the first len
elements and dropping the rest.
If len
is greater than the map’s current length, this has no effect.
Clears the IndexMap
in the given index range, returning those
key-value pairs as a drain iterator.
The range may be any type that implements RangeBounds<usize>
,
including all of the std::ops::Range*
types, or even a tuple pair of
Bound
start and end values. To drain the map entirely, use RangeFull
like map.drain(..)
.
This shifts down all entries following the drained range to fill the gap, and keeps the allocated memory for reuse.
Panics if the starting point is greater than the end point or if the end point is greater than the length of the map.
Splits the collection into two at the given index.
Returns a newly allocated map containing the elements in the range
[at, len)
. After the call, the original map will be left containing
the elements [0, at)
with its previous capacity unchanged.
Panics if at > len
.
Reserve capacity for additional
more key-value pairs.
Computes in O(n) time.
Shrink the capacity of the map as much as possible.
Computes in O(n) time.
Insert a key-value pair in the map.
If an equivalent key already exists in the map: the key remains and
retains in its place in the order, its corresponding value is updated
with value
and the older value is returned inside Some(_)
.
If no equivalent key existed in the map: the new key-value pair is
inserted, last in order, and None
is returned.
Computes in O(1) time (amortized average).
See also entry
if you you want to insert or modify
or if you need to get the index of the corresponding key-value pair.
Insert a key-value pair in the map, and get their index.
If an equivalent key already exists in the map: the key remains and
retains in its place in the order, its corresponding value is updated
with value
and the older value is returned inside (index, Some(_))
.
If no equivalent key existed in the map: the new key-value pair is
inserted, last in order, and (index, None)
is returned.
Computes in O(1) time (amortized average).
See also entry
if you you want to insert or modify
or if you need to get the index of the corresponding key-value pair.
Get the given key’s corresponding entry in the map for insertion and/or in-place manipulation.
Computes in O(1) time (amortized average).
Return true
if an equivalent to key
exists in the map.
Computes in O(1) time (average).
Return a reference to the value stored for key
, if it is present,
else None
.
Computes in O(1) time (average).
Return references to the key-value pair stored for key
,
if it is present, else None
.
Computes in O(1) time (average).
Return item index, key and value
Return item index, if it exists in the map
Computes in O(1) time (average).
pub fn get_full_mut<Q: ?Sized>(
&mut self,
key: &Q
) -> Option<(usize, &K, &mut V)> where
Q: Hash + Equivalent<K>,
Remove the key-value pair equivalent to key
and return
its value.
NOTE: This is equivalent to .swap_remove(key)
, if you need to
preserve the order of the keys in the map, use .shift_remove(key)
instead.
Computes in O(1) time (average).
pub fn remove_entry<Q: ?Sized>(&mut self, key: &Q) -> Option<(K, V)> where
Q: Hash + Equivalent<K>,
pub fn remove_entry<Q: ?Sized>(&mut self, key: &Q) -> Option<(K, V)> where
Q: Hash + Equivalent<K>,
Remove and return the key-value pair equivalent to key
.
NOTE: This is equivalent to .swap_remove_entry(key)
, if you need to
preserve the order of the keys in the map, use .shift_remove_entry(key)
instead.
Computes in O(1) time (average).
Remove the key-value pair equivalent to key
and return
its value.
Like Vec::swap_remove
, the pair is removed by swapping it with the
last element of the map and popping it off. This perturbs
the position of what used to be the last element!
Return None
if key
is not in map.
Computes in O(1) time (average).
pub fn swap_remove_entry<Q: ?Sized>(&mut self, key: &Q) -> Option<(K, V)> where
Q: Hash + Equivalent<K>,
pub fn swap_remove_entry<Q: ?Sized>(&mut self, key: &Q) -> Option<(K, V)> where
Q: Hash + Equivalent<K>,
Remove and return the key-value pair equivalent to key
.
Like Vec::swap_remove
, the pair is removed by swapping it with the
last element of the map and popping it off. This perturbs
the position of what used to be the last element!
Return None
if key
is not in map.
Computes in O(1) time (average).
pub fn swap_remove_full<Q: ?Sized>(&mut self, key: &Q) -> Option<(usize, K, V)> where
Q: Hash + Equivalent<K>,
pub fn swap_remove_full<Q: ?Sized>(&mut self, key: &Q) -> Option<(usize, K, V)> where
Q: Hash + Equivalent<K>,
Remove the key-value pair equivalent to key
and return it and
the index it had.
Like Vec::swap_remove
, the pair is removed by swapping it with the
last element of the map and popping it off. This perturbs
the position of what used to be the last element!
Return None
if key
is not in map.
Computes in O(1) time (average).
Remove the key-value pair equivalent to key
and return
its value.
Like Vec::remove
, the pair is removed by shifting all of the
elements that follow it, preserving their relative order.
This perturbs the index of all of those elements!
Return None
if key
is not in map.
Computes in O(n) time (average).
pub fn shift_remove_entry<Q: ?Sized>(&mut self, key: &Q) -> Option<(K, V)> where
Q: Hash + Equivalent<K>,
pub fn shift_remove_entry<Q: ?Sized>(&mut self, key: &Q) -> Option<(K, V)> where
Q: Hash + Equivalent<K>,
Remove and return the key-value pair equivalent to key
.
Like Vec::remove
, the pair is removed by shifting all of the
elements that follow it, preserving their relative order.
This perturbs the index of all of those elements!
Return None
if key
is not in map.
Computes in O(n) time (average).
pub fn shift_remove_full<Q: ?Sized>(&mut self, key: &Q) -> Option<(usize, K, V)> where
Q: Hash + Equivalent<K>,
pub fn shift_remove_full<Q: ?Sized>(&mut self, key: &Q) -> Option<(usize, K, V)> where
Q: Hash + Equivalent<K>,
Remove the key-value pair equivalent to key
and return it and
the index it had.
Like Vec::remove
, the pair is removed by shifting all of the
elements that follow it, preserving their relative order.
This perturbs the index of all of those elements!
Return None
if key
is not in map.
Computes in O(n) time (average).
Remove the last key-value pair
This preserves the order of the remaining elements.
Computes in O(1) time (average).
Scan through each key-value pair in the map and keep those where the
closure keep
returns true
.
The elements are visited in order, and remaining elements keep their order.
Computes in O(n) time (average).
Sort the map’s key-value pairs by the default ordering of the keys.
See sort_by
for details.
Sort the map’s key-value pairs in place using the comparison
function cmp
.
The comparison function receives two key and value pairs to compare (you can sort by keys or values or their combination as needed).
Computes in O(n log n + c) time and O(n) space where n is the length of the map and c the capacity. The sort is stable.
Sort the key-value pairs of the map and return a by-value iterator of the key-value pairs with the result.
The sort is stable.
Sort the map’s key-value pairs by the default ordering of the keys, but may not preserve the order of equal elements.
See sort_unstable_by
for details.
Sort the map’s key-value pairs in place using the comparison function cmp
, but
may not preserve the order of equal elements.
The comparison function receives two key and value pairs to compare (you can sort by keys or values or their combination as needed).
Computes in O(n log n + c) time where n is the length of the map and c is the capacity. The sort is unstable.
Sort the key-value pairs of the map and return a by-value iterator of the key-value pairs with the result.
The sort is unstable.
Get a key-value pair by index
Valid indices are 0 <= index < self.len()
Computes in O(1) time.
Get a key-value pair by index
Valid indices are 0 <= index < self.len()
Computes in O(1) time.
Get the first key-value pair, with mutable access to the value
Computes in O(1) time.
Get the last key-value pair, with mutable access to the value
Computes in O(1) time.
Remove the key-value pair by index
Valid indices are 0 <= index < self.len()
Like Vec::swap_remove
, the pair is removed by swapping it with the
last element of the map and popping it off. This perturbs
the position of what used to be the last element!
Computes in O(1) time (average).
Remove the key-value pair by index
Valid indices are 0 <= index < self.len()
Like Vec::remove
, the pair is removed by shifting all of the
elements that follow it, preserving their relative order.
This perturbs the index of all of those elements!
Computes in O(n) time (average).
Swaps the position of two key-value pairs in the map.
Panics if a
or b
are out of bounds.
Trait Implementations
Extend the map with all key-value pairs in the iterable.
See the first extend method for more details.
extend_one
)Extends a collection with exactly one element.
extend_one
)Reserves capacity in a collection for the given number of additional elements. Read more
Extend the map with all key-value pairs in the iterable.
This is equivalent to calling insert
for each of
them in order, which means that for keys that already existed
in the map, their value is updated but it keeps the existing order.
New keys are inserted in the order they appear in the sequence. If equivalents of a key occur more than once, the last corresponding value prevails.
extend_one
)Extends a collection with exactly one element.
extend_one
)Reserves capacity in a collection for the given number of additional elements. Read more
impl<K, V, S> FromIterator<(K, V)> for IndexMap<K, V, S> where
K: Hash + Eq,
S: BuildHasher + Default,
impl<K, V, S> FromIterator<(K, V)> for IndexMap<K, V, S> where
K: Hash + Eq,
S: BuildHasher + Default,
impl<K, V, Q: ?Sized, S> Index<&'_ Q> for IndexMap<K, V, S> where
Q: Hash + Equivalent<K>,
K: Hash + Eq,
S: BuildHasher,
impl<K, V, Q: ?Sized, S> Index<&'_ Q> for IndexMap<K, V, S> where
Q: Hash + Equivalent<K>,
K: Hash + Eq,
S: BuildHasher,
Access IndexMap
values corresponding to a key.
Examples
use indexmap::IndexMap;
let mut map = IndexMap::new();
for word in "Lorem ipsum dolor sit amet".split_whitespace() {
map.insert(word.to_lowercase(), word.to_uppercase());
}
assert_eq!(map["lorem"], "LOREM");
assert_eq!(map["ipsum"], "IPSUM");
use indexmap::IndexMap;
let mut map = IndexMap::new();
map.insert("foo", 1);
println!("{:?}", map["bar"]); // panics!
Access IndexMap
values at indexed positions.
Examples
use indexmap::IndexMap;
let mut map = IndexMap::new();
for word in "Lorem ipsum dolor sit amet".split_whitespace() {
map.insert(word.to_lowercase(), word.to_uppercase());
}
assert_eq!(map[0], "LOREM");
assert_eq!(map[1], "IPSUM");
map.reverse();
assert_eq!(map[0], "AMET");
assert_eq!(map[1], "SIT");
map.sort_keys();
assert_eq!(map[0], "AMET");
assert_eq!(map[1], "DOLOR");
use indexmap::IndexMap;
let mut map = IndexMap::new();
map.insert("foo", 1);
println!("{:?}", map[10]); // panics!
impl<K, V, Q: ?Sized, S> IndexMut<&'_ Q> for IndexMap<K, V, S> where
Q: Hash + Equivalent<K>,
K: Hash + Eq,
S: BuildHasher,
impl<K, V, Q: ?Sized, S> IndexMut<&'_ Q> for IndexMap<K, V, S> where
Q: Hash + Equivalent<K>,
K: Hash + Eq,
S: BuildHasher,
Access IndexMap
values corresponding to a key.
Mutable indexing allows changing / updating values of key-value pairs that are already present.
You can not insert new pairs with index syntax, use .insert()
.
Examples
use indexmap::IndexMap;
let mut map = IndexMap::new();
for word in "Lorem ipsum dolor sit amet".split_whitespace() {
map.insert(word.to_lowercase(), word.to_string());
}
let lorem = &mut map["lorem"];
assert_eq!(lorem, "Lorem");
lorem.retain(char::is_lowercase);
assert_eq!(map["lorem"], "orem");
use indexmap::IndexMap;
let mut map = IndexMap::new();
map.insert("foo", 1);
map["bar"] = 1; // panics!
Access IndexMap
values at indexed positions.
Mutable indexing allows changing / updating indexed values that are already present.
You can not insert new values with index syntax, use .insert()
.
Examples
use indexmap::IndexMap;
let mut map = IndexMap::new();
for word in "Lorem ipsum dolor sit amet".split_whitespace() {
map.insert(word.to_lowercase(), word.to_string());
}
let lorem = &mut map[0];
assert_eq!(lorem, "Lorem");
lorem.retain(char::is_lowercase);
assert_eq!(map["lorem"], "orem");
use indexmap::IndexMap;
let mut map = IndexMap::new();
map.insert("foo", 1);
map[10] = 1; // panics!
Opt-in mutable access to keys.
See MutableKeys
for more information.
type Key = K
type Value = V
Return item index, mutable reference to key and value
Scan through each key-value pair in the map and keep those where the
closure keep
returns true
. Read more
This method is not useful in itself – it is there to “seal” the trait for external implementation, so that we can add methods without causing breaking changes. Read more
impl<K, V1, S1, V2, S2> PartialEq<IndexMap<K, V2, S2>> for IndexMap<K, V1, S1> where
K: Hash + Eq,
V1: PartialEq<V2>,
S1: BuildHasher,
S2: BuildHasher,
impl<K, V1, S1, V2, S2> PartialEq<IndexMap<K, V2, S2>> for IndexMap<K, V1, S1> where
K: Hash + Eq,
V1: PartialEq<V2>,
S1: BuildHasher,
S2: BuildHasher,
Auto Trait Implementations
impl<K, V, S> RefUnwindSafe for IndexMap<K, V, S> where
K: RefUnwindSafe,
S: RefUnwindSafe,
V: RefUnwindSafe,
impl<K, V, S> UnwindSafe for IndexMap<K, V, S> where
K: UnwindSafe,
S: UnwindSafe,
V: UnwindSafe,
Blanket Implementations
Mutably borrows from an owned value. Read more