etl/docs/containers/maps/const-map.md

title
const_map / const_map_ext

{{< callout >}} Header: const_map.h
Since: TBC
Similar to: std::map {{< /callout >}}

A fixed capacity read-only map based on a sorted array. The containers are designed to be able to be constexpr for C++14 and up.

The interface is most similar to std::map. Uses etl::less as the default key comparison method.

etl::const_map<typename TKey, typename TMapped, size_t Size, TKeyCompare = etl::less>
etl::const_map_ext<typename TKey, typename TMapped, TKeyCompare = etl::less>

Inherits from etl::iconst_map<TKey, TMapped, TKeyCompare>
etl::iconst_map may be used as a Size independent pointer or reference type for any etl::const_map instance.
Both the key type and mapped type must be default constructible.

Template deduction guides

C++17 and above

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

Example

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

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

---

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

Example

constexpr etl::pair<int, int> values[]{ etl::pair{0, 1}, etl::pair{2, 3}, 
                                        etl::pair{4, 5}, etl::pair{6, 7} };

constexpr etl::const_map_ext data{ values };

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

constexpr values[]{ etl::pair{0, 1}, etl::pair{2, 3}, 
                    etl::pair{4, 5}, etl::pair{6, 7} };
constexpr etl::span<const etl::pair<int, int>, 4> span{ values };
constexpr etl::const_map_ext data{ span };

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

Member types

Type	Maps to	Description
key_type	TKey	Must be default constructible.
mapped_type	TMapped	Must be default constructible.
value_type	pair<const key_type, mapped_type>	The type is either std::pair (default) or etl::pair (ETL_NO_STL)
size_type	std::size_t
difference_type	std::ptrdiff_t
const_reference	const T&
const_pointer	const T*
const_iterator		Constant random access iterator

Constructor

template <typename... TElements>
ETL_CONSTEXPR14 explicit const_map(TElements&&... elements) ETL_NOEXCEPT

Construct a const_map from a variadic list of elements.
Static asserts if the elements are not of type value_type.
Static asserts if the number of elements is greater than the capacity of the const_map.

Element access

ETL_CONSTEXPR14 const TMapped& at(key_parameter_t key) const ETL_NOEXCEPT

Description
Returns a const reference to the indexed element.

ETL_CONSTEXPR14 const TMapped& operator[](key_parameter_t key) const ETL_NOEXCEPT

Description
Returns a const reference to the indexed element.

Iterators

const_iterator begin() const ETL_NOEXCEPT
const_iterator cbegin() const ETL_NOEXCEPT

Description
Returns an iterator to the beginning of the map.

const_iterator end() const ETL_NOEXCEPT
const_iterator cend() const ETL_NOEXCEPT

Description
Returns an iterator to the end of the map.

Capacity

ETL_CONSTEXPR14 bool empty() const ETL_NOEXCEPT

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

ETL_CONSTEXPR14 bool full() const ETL_NOEXCEPT

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

ETL_CONSTEXPR14 size_t size() const ETL_NOEXCEPT

Description
Returns the size of the lookup.

ETL_CONSTEXPR14 size_t max_size() const ETL_NOEXCEPT

Description
Returns the maximum possible Size of the map.

Status

ETL_CONSTEXPR14 bool is_valid() const ETL_NOEXCEPT

Description
Check that the elements are valid for a map.
The elements must be sorted and contain no duplicates.

Search

ETL_CONSTEXPR14 const_iterator find(const key_type& key) const ETL_NOEXCEPT

ETL_CONSTEXPR14 const_iterator lower_bound(const key_type& key) const ETL_NOEXCEPT

ETL_CONSTEXPR14 const_iterator upper_bound(const key_type& key) const ETL_NOEXCEPT

ETL_CONSTEXPR14 pair<const_iterator, const_iterator> equal_range(const key_type& key) const ETL_NOEXCEPT

Description
The return type is either std::pair (default) or etl::pair (ETL_NO_STL)

ETL_CONSTEXPR14 bool contains(const key_type& k) const ETL_NOEXCEPT

Description
Check if the container contains the key.

---

For comparators that define is_transparent.

template <typename K>
ETL_CONSTEXPR14 const_iterator find(const K& key) const ETL_NOEXCEPT

template <typename K>
ETL_CONSTEXPR14 const_iterator lower_bound(const K& key) const ETL_NOEXCEPT

template <typename K>
ETL_CONSTEXPR14 const_iterator upper_bound(const K& key) const ETL_NOEXCEPT

template <typename K>
ETL_CONSTEXPR14 pair<const_iterator, const_iterator> equal_range(const K& key) const ETL_NOEXCEPT

template <typename K>
ETL_CONSTEXPR14 bool contains(const K& k) const ETL_NOEXCEPT

Description
Check if the container contains the key.

Non-member functions

Lexicographically comparisons

Operator	Description
==	true if the contents of the maps are equal, otherwise false.
!=	true if the contents of the maps are not equal, otherwise false.
<	true if the contents of the lhs is less-than the rhs, otherwise false.
<=	true if the contents of the lhs is less-than-equal the rhs, otherwise false.
>	true if the contents of the lhs is greater-than the rhs, otherwise false.
>=	true if the contents of the lhs is greater-than-equal the rhs, otherwise false.

Technical stuff

The const map is implemented as a sorted array key/value pairs.