etl/docs/containers/maps/unordered-multimap.md

title
unordered_multimap

{{< callout type="info">}} Header: unordered_multimap.h
Similar to: std::unordered_multimap {{< /callout >}}

A fixed capacity unordered map. Uses std::less as the default key comparison method.

template <typename TKey, 
          typename TValue, 
          size_t   MAX_SIZE, 
          size_t   MAX_BUCKETS = MAX_SIZE, 
          typename THash = etl::hash<TKey>, 
          typename TKeyEqual = etl::equal_to<TKey>>
class unordered_multimap

Inherits from iunordered_map<TKey, TValue, THash, TKeyEqual>.
etl::iunordered_map may be used as a size independent pointer or reference type for any etl::unordered_multimap instance.

Template deduction guides

C++17 and above

template <typename... TPairs>
etl::unordered_multimap(TPairs...)

Example

etl::unordered_multimap data{ etl::pair{0, 1}, etl::pair{2, 3}, etl::pair{4, 5}, etl::pair{6, 7} };

Defines data as an unordered map of int/int pairs, of length 4, containing the supplied data.

Make template

C++11 and above

template <typename TKey, 
          typename TValue, 
          typename THash       = etl::hash<TKey>, 
          typename TKeyEqual   = etl::equal_to<TKey>
          typename... TPairs>
constexpr auto make_unordered_map(TValues&&... values)

Example

auto data = etl::make_unordered_map<int, int>(etl::pair{0, 1}, etl::pair{2, 3}, 
                                              etl::pair{4, 5}, etl::pair{6, 7});

Member types

value_type              pair<const TKey, T>
key_type                The type of the key value
mapped_type             The type of the mapped value
hasher                  The type used to hash the key
key_equal               The functor used to compare keys
reference               A reference to a value_type
const_reference         A reference to a const value_type
pointer                 A pointer to a value_type
const_pointer           A pointer to a const value_type
size_type               The type used for size information
iterator                Random access iterator
const_iterator          Constant random access iterator
local_iterator          Iterator to a bucket
local_const_iterator    A const iterator to a bucket

Constructor

unordered_multimap()

Description
Default constructor

---

unordered_multimap(const unordered_multimap& other)

Description
Copy constructor

---

template <typename TIterator>
unordered_multimap(TIterator begin, TIterator end)

Description
Construct from a range

Element access

mapped_type& at(key_parameter_t key)
const mapped_type& at(key_parameter_t key) const

Description
Returns a reference or const reference to the indexed element.
Raises an etl::unordered_map_out_of_range if the key is not in the table.
If assert or exceptions are not enabled then undefined behaviour occurs.

---

mapped_type& operator[](key_parameter_t key)

Description
Returns a reference to the indexed element.
If the key does not exist then one is created using the default constructor.
If the map is full then emits an etl::unordered_map_full.
If asserts or exceptions are not enabled then undefined behaviour occurs.

---

iterator find(key_parameter_t key);
const_iterator find (key_parameter_t key) const

Description
Searches the container for an element with a key equivalent to key and returns an iterator to it if found, otherwise it returns an iterator to etl::unordered_multimap::end().

---

bool contains(const_key_reference key) const

Description
Check if the map contains the key.

---

template <typename K, typename KE = TKeyEqual>
bool contains(const K& key) const

Description
Check if the map contains the key.
Enabled if the comparator is transparent.

---

size_type count(key_parameter_t key) const

Description
Count elements with a specific key.
Searches the container for elements with a key equivalent to key and returns the number of matches

---

iterator lower_bound(key_parameter_t key)
const_iterator lower_bound(key_parameter_t key) const

Description
Returns an iterator pointing to the first element in the container whose key is not considered to go before key (i.e., either it is equivalent or goes after).

---

iterator upper_bound(key_parameter_t key)
const_iterator upper_bound(key_parameter_t key) const

Description
Returns an iterator pointing to the first element in the container whose key is considered to go after key.

---

pair<iterator, iterator> equal_range(key_parameter_t key)
pair<const_iterator, const_iterator> equal_range(key_parameter_t key) const

Description
Returns the bounds of a range that includes all the elements in the container which have a key equivalent to key.

Iterators

iterator begin()
const_iterator begin() const
const_iterator cbegin() const

Description
Returns an iterator to the beginning of the map.

---

iterator end()
const_iterator end() const
const_iterator cend() const

Description
Returns an iterator to the end of the map.

Capacity

bool empty() const

Description
Returns true if the size of the map is zero, otherwise false.

---

bool full() const

Description
Returns true if the size of the map is SIZE, otherwise false.

---

size_t size() const

Description
Returns the size of the map.

---

size_t max_size() const

Description
Returns the maximum possible size of the map.

---

size_t available() const

Description
Returns the remaining available capacity in the map.

---

size_type get_bucket_index(key_parameter_t key) const

Description
Returns the bucket index for the key.

---

size_type bucket_size(key_parameter_t key) const

Description
Returns the size of the bucket key.

---

size_type max_bucket_count() const

Description
Returns the maximum number of the buckets the container can hold.

---

float load_factor() const

Description
Returns the load factor = size / bucket_count

---

hasher hash_function() const

Description
Returns the function that hashes the keys.

---

key_equal key_eq() const

Description
Returns the function that compares the keys.

Modifiers

template <typename TIterator>
void assign(TIterator first, TIterator last)

Description
Assigns elements from the range [first, last)].
Clears the container before assigning.

---

pair<iterator, bool> insert(const value_type& key_value_pair)
iterator insert(const_iterator, const value_type& key_value_pair)

Description
Assigns elements from the range [first, last)].
Clears the container before assigning.

---

template <template TIterator>
void insert(TIterator first, TIterator last)

Description
Inserts the range [first, last)] into the map.
If the map is full then emits an etl::unordered_map_full error.
If asserts or exceptions are not enabled then undefined behaviour occurs.

---

size_t erase(key_parameter_t key)

Description
Removes the element with the key key.

---

iterator erase(const_iterator ielement)

Description
Removes the element with the key key.

---

iterator erase(const_iterator first, const_iterator last)

Description
Erases values in the map.
Iterator are not checked for validity.

---

void clear()

Description
Clears the map to a size of zero.

Non-member functions

operator ==

Description
true if the contents of the maps are equal, otherwise false.

---

operator !=

Description
true if the contents of the maps are not equal, otherwise false.