A C++ template library for embedded applications
MIT licensed
Designed and
maintained by
John Wellbelove
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reference_flat_set

reference_flat_multiset


A fixed capacity set based on a sorted vector.
The container stores references to objects, rather than the objects themselves.
The container is an associative lookup table with O(N) insertion and erase, and O(log N) search.
This container is best used for tables that are occasionally updated and spend most of their time being searched.
The interface is most similar to std::set.
Uses etl::less as the default key comparison method.

etl::reference_flat_set<typename T, const size_t SIZE, TCompare = etl::less>

Inherits from etl::ireference_flat_set<T, TCompare>
etl::ireference_flat_set may be used as a size independent pointer or reference type for any
etl::reference_flat_set instance.

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Template deduction guides
C++17 and above

template <typename... T>
etl::reference_flat_set(T...)

Example
etl::reference_flat_setdata{ 0, 1, 2, 3, 4, 5, 6, 7 };
Defines data as a set of int/int pairs, of length 8, containing the supplied data.
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Make template
C++11 and above
template <typename TKey
          typename... T>
constexpr auto make_reference_flat_set(T&&... values)

Example
auto data = etl::make_reference_flat_set<int>(0, 1, 2, 3, 4, 5, 6, 7);

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Member types


key_type                T
value_type              T
size_type               size_t
difference_type         ptrdiff_t
reference               value_type&
const_reference         const value_type&
pointer                 value_type*
const_pointer           const value_type*
iterator                Random access iterator
const_iterator          Constant random access iterator
reverse_iterator        ETL_OR_STD:reverse_iterator<iterator>
const_reverse_iterator  ETL_OR_STD::reverse_iterator<const_iterator>

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Constructor

etl::flat_set<T, SIZE, TCompare>();

etl::flat_set(const flat_set& other)

template <typename TIterator>
etl::flat_set<T, SIZE, TCompare>(TIterator begin, TIterator end);
If the set is full then emits an etl::reference_flat_set_full. If asserts or exceptions are not enabled then undefined
behaviour occurs.

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Iterators

iterator begin()
const_iterator begin() const
const_iterator cbegin() const
Returns an iterator to the beginning of the set.
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iterator end()
const_iterator end() const
const_iterator cend() const
Returns an iterator to the end of the set.
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iterator rbegin()
const_iterator rbegin() const
const_iterator crbegin() const
Returns a reverse iterator to the beginning of the set.
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iterator rend()
const_iterator rend() const
const_iterator crend() const
Returns a reverse iterator to the end of the set.
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Capacity


bool empty() const
Returns true if the size of the set is zero, otherwise false.
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bool full() const
Returns true if the size of the lookup is SIZE, otherwise false.
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size_t size() const
Returns the size of the lookup.
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size_t max_size() const
Returns the maximum possible size of the set.
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size_t available() const
Returns the remaining available capacity in the set.
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Modifiers


flat_set& operator = (const flat_set& rhs)
Copies the data from another flat set.
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ETL_OR_STD::pair<iterator, bool> insert(const value_type& value)
iterator insert(iterator position, const value_type& value)

template <typename TIterator>
void insert(TIterator first, TIterator last)
Inserts values in to the set.
If the set is full then emits an etl::reference_flat_set_full. If asserts or exceptions are not enabled then undefined
behaviour occurs.
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size_t erase(key_value_parameter_t key)
void erase(iterator i_element)
void erase(iterator first, iterator last)
Erases values in the set.
Iterators are not checked for validity.

20.21.0
template <typename K>
size_t erase(K&& key)
Erases values in the map.
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void clear();
Clears the lookup to a size of zero.
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Search


iterator find(key_value_parameter_t key)
const_iterator find(key_value_parameter_t key) const
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iterator lower_bound(key_value_parameter_t key)
const_iterator lower_bound(key_value_parameter_t key) const
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iterator upper_bound(key_value_parameter_t key)
const_iterator upper_bound(key_value_parameter_t key) const
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ETL_OR_STD::pair<iterator, iterator> equal_range(key_value_parameter_t key)
ETL_OR_STD::pair<const_iterator, const_iterator> equal_range(key_value_parameter_t key) const
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20.21.0
C++11 or above
For comparators that define is_transparent.

template <typename K>
iterator find(const K& key)

template <typename K>
const_iterator find(const K& key) const
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20.21.0
C++11 or above
template <typename K>
iterator lower_bound(const K& key)

template <typename K>
const_iterator lower_bound(const K& key) const
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20.21.0
C++11 or above
template <typename K>
iterator upper_bound(const K& key)

template <typename K>
const_iterator upper_bound(const K& key) const
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20.21.0
C++11 or above
template <typename K>
pair<iterator, iterator> equal_range(const K& key)

template <typename K>
pair<const_iterator, const_iterator> equal_range(const K& key) const
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20.21.0
bool contains(key_value_parameter_t key) const
Check if the container contains the key.

20.21.0
C++11 or above
For comparators that define is_transparent.
template <typename K>
bool contains(const K& k) const
Check if the container contains the key.
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Non-member functions

Lexicographically comparisons


==  true if the contents of the sets are equal, otherwise false.
!=  true if the contents of the sets are not equal, otherwise false.
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How it works


Reference flat sets are different from the normal version in that the elements are not copied, but linked directly.
This means that the lifetime of the element inserted must be as great as that of the set that contains it.
Unlike most other reference containers, the set has a finite capacity.


Flat sets are usually implemented internally as a sorted vector of values. Whilst this makes searching fast, it can have a
detrimental effect when items are inserted into a container that stores complex, non-trivial values.
As Inserting requires that all of the items above the insert position must be shifted, this can become an expensive
operation for larger containers.

To improve insertion performance ETL reference flat sets are implemented as vectors of pointers to values, sorted by
value. An insertion will involve a copy of a range of pointers; an operation that can be made very fast.

The downside is that access to an item via an iterator will involve one indirection and the overhead of the container will
be one pointer per item. A normal flat set implementation does not have this overhead.

intrusive_flat_set.h / reference_flat_multiset.h