c8bc1bd896
* Corrected the documented make_xxx factory signatures and examples
The Make template sections across the container documentation had
drifted from the implementations, largely through copy-paste:
- map.md, multimap.md and flat-multimap.md all documented
make_flat_map; multiset.md documented make_set; flat-multiset.md
documented make_flat_set; unordered-multimap.md documented
make_unordered_map. Names and examples now match each container.
- Every signature omitted the C++11-required trailing return type
despite the sections being labelled C++11 and above; several also
used a parameter name (TValues) that did not match any template
parameter, and the unordered map headers were missing a comma.
- forward-list.md documented a make_array-style signature with an
explicit element type; the real function deduces the element type as
the common type of the arguments, as documented for make_list.
- The flat_set/flat_multiset template headers were missing the
variadic parameter pack, and their examples passed a braced list to
a variadic function, which does not compile; set.md used TKeyCompare
where the implementation uses TCompare.
- deque.md and the reference container docs were missing code fences.
- Updated the four reference_flat_* function. However these functions
cannot be instantiated at all (the reference containers have no
initializer_list constructor, since one would dangle by design), so
the documented examples have never compiled.
Every remaining documented example verified to compile with clang 22
(C++17) against the current headers.
* Fixed C++17-only syntax in factory examples and flagged the non-compilable ones
Review feedback on the make_xxx documentation examples:
- All the map-family factory examples are labelled C++11 and above but
constructed their pairs with class template argument deduction
(etl::pair{0, 1}), which requires C++17. The pairs in the make_flat_map,
make_flat_multimap, make_map, make_multimap, make_unordered_map,
make_unordered_multimap, make_reference_flat_map and
make_reference_flat_multimap examples now name their template arguments
explicitly. The template deduction guide examples are unchanged, as
those sections are labelled C++17 and above. Verified with clang 22 in
C++14 mode, which, like C++11, has no deduction guides.
- The four make_reference_flat_* examples are now preceded by a warning
callout stating that they do not currently compile: the functions
cannot be instantiated because the reference containers have no
initializer_list constructor. The examples themselves are retained,
rewritten to pass named lvalues rather than temporaries, since the
reference containers store references to external objects and the
temporaries would dangle even if the functions compiled. The defect
is being reported separately.
---------
Co-authored-by: John Wellbelove <jwellbelove@users.noreply.github.com>
7.9 KiB
| title |
|---|
| unordered_map |
{{< callout type="info">}}
Header: unordered_map.h
Similar to: std::unordered_map
{{< /callout >}}
A fixed capacity unordered map.
Uses std::less as the default key comparison method.
This page just describes etl::unordered_map.
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_map
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_map instance.
Template deduction guides
C++17 and above
template <typename... TPairs>
etl::unordered_map(TPairs...)
Example
etl::unordered_map 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 T,
typename THash = etl::hash<TKey>,
typename TKeyEqual = etl::equal_to<TKey>,
typename... TPairs>
constexpr auto make_unordered_map(TPairs&&... pairs) -> etl::unordered_map<TKey, T, sizeof...(TPairs), sizeof...(TPairs), THash, TKeyEqual>
Example
auto data = etl::make_unordered_map<int, int>(etl::pair<int, int>{0, 1}, etl::pair<int, int>{2, 3},
etl::pair<int, int>{4, 5}, etl::pair<int, int>{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_map()
Description
Default constructor
unordered_map(const unordered_map& other)
Description
Copy constructor
template <typename TIterator>
unordered_map(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_map::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.