reference_flat_map.h

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/******************************************************************************
The MIT License(MIT)
 
Embedded Template Library.
https://github.com/ETLCPP/etl
https://www.etlcpp.com
 
Copyright(c) 2017 John Wellbelove
 
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files(the "Software"), to deal
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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#ifndef ETL_REFERENCE_FLAT_MAP_INCLUDED
#define ETL_REFERENCE_FLAT_MAP_INCLUDED
 
#include "platform.h"
#include "debug_count.h"
#include "error_handler.h"
#include "exception.h"
#include "iterator.h"
#include "nth_type.h"
#include "optional.h"
#include "parameter_type.h"
#include "static_assert.h"
#include "type_traits.h"
#include "vector.h"
 
#include "private/comparator_is_transparent.h"
 
#include <stddef.h>
 
//*****************************************************************************
//*****************************************************************************
 
namespace etl
{
  //***************************************************************************
  //***************************************************************************
  class flat_map_exception : public etl::exception
  {
  public:
 
    flat_map_exception(string_type reason_, string_type file_name_, numeric_type line_number_)
      : exception(reason_, file_name_, line_number_)
    {
    }
  };
 
  //***************************************************************************
  //***************************************************************************
  class flat_map_full : public etl::flat_map_exception
  {
  public:
 
    flat_map_full(string_type file_name_, numeric_type line_number_)
      : flat_map_exception(ETL_ERROR_TEXT("flat_map: full", ETL_REFERENCE_FLAT_MAP_FILE_ID"A"), file_name_, line_number_)
    {
    }
  };
 
  //***************************************************************************
  //***************************************************************************
  class flat_map_out_of_bounds : public etl::flat_map_exception
  {
  public:
 
    flat_map_out_of_bounds(string_type file_name_, numeric_type line_number_)
      : flat_map_exception(ETL_ERROR_TEXT("flat_map:bounds", ETL_REFERENCE_FLAT_MAP_FILE_ID"B"), file_name_, line_number_)
    {
    }
  };
 
  //***************************************************************************
  //***************************************************************************
  template <typename TKey, typename TMapped, typename TKeyCompare = etl::less<TKey> >
  class ireference_flat_map
  {
  public:
 
    typedef ETL_OR_STD::pair<const TKey, TMapped> value_type;
 
  protected:
 
    typedef etl::ivector<value_type*> lookup_t;
 
  public:
 
    typedef TKey              key_type;
    typedef TMapped           mapped_type;
    typedef TKeyCompare       key_compare;
    typedef value_type&       reference;
    typedef const value_type& const_reference;
    typedef value_type*       pointer;
    typedef const value_type* const_pointer;
    typedef size_t            size_type;
 
    class const_iterator;
 
    //*************************************************************************
    class iterator : public etl::iterator<ETL_OR_STD::bidirectional_iterator_tag, value_type>
    {
    public:
 
      friend class ireference_flat_map;
      friend class ireference_flat_map::const_iterator;
 
      iterator() {}
 
      iterator(typename lookup_t::iterator ilookup_)
        : ilookup(ilookup_)
      {
      }
 
      iterator(const iterator& other)
        : ilookup(other.ilookup)
      {
      }
 
      iterator& operator=(const iterator& other)
      {
        ilookup = other.ilookup;
        return *this;
      }
 
      iterator& operator++()
      {
        ++ilookup;
        return *this;
      }
 
      iterator operator++(int)
      {
        iterator temp(*this);
        ++ilookup;
        return temp;
      }
 
      iterator& operator--()
      {
        --ilookup;
        return *this;
      }
 
      iterator operator--(int)
      {
        iterator temp(*this);
        --ilookup;
        return temp;
      }
 
      reference operator*() const
      {
        return *(*ilookup);
      }
 
      pointer operator&() const
      {
        return etl::addressof(*(*ilookup));
      }
 
      pointer operator->() const
      {
        return etl::addressof(*(*ilookup));
      }
 
      friend bool operator==(const iterator& lhs, const iterator& rhs)
      {
        return lhs.ilookup == rhs.ilookup;
      }
 
      friend bool operator!=(const iterator& lhs, const iterator& rhs)
      {
        return !(lhs == rhs);
      }
 
    private:
 
      typename lookup_t::iterator ilookup;
    };
 
    //*************************************************************************
    class const_iterator : public etl::iterator<ETL_OR_STD::bidirectional_iterator_tag, const value_type>
    {
    public:
 
      friend class ireference_flat_map;
 
      const_iterator() {}
 
      const_iterator(typename lookup_t::const_iterator ilookup_)
        : ilookup(ilookup_)
      {
      }
 
      const_iterator(const typename ireference_flat_map::iterator& other)
        : ilookup(other.ilookup)
      {
      }
 
      const_iterator(const const_iterator& other)
        : ilookup(other.ilookup)
      {
      }
 
      const_iterator& operator=(const typename ireference_flat_map::iterator& other)
      {
        ilookup = other.ilookup;
        return *this;
      }
 
      const_iterator& operator=(const const_iterator& other)
      {
        ilookup = other.ilookup;
        return *this;
      }
 
      const_iterator& operator++()
      {
        ++ilookup;
        return *this;
      }
 
      const_iterator operator++(int)
      {
        const_iterator temp(*this);
        ++ilookup;
        return temp;
      }
 
      const_iterator& operator--()
      {
        --ilookup;
        return *this;
      }
 
      const_iterator operator--(int)
      {
        const_iterator temp(*this);
        --ilookup;
        return temp;
      }
 
      const_reference operator*() const
      {
        return *(*ilookup);
      }
 
      const_pointer operator&() const
      {
        return etl::addressof(*(*ilookup));
      }
 
      const_pointer operator->() const
      {
        return etl::addressof(*(*ilookup));
      }
 
      friend bool operator==(const const_iterator& lhs, const const_iterator& rhs)
      {
        return lhs.ilookup == rhs.ilookup;
      }
 
      friend bool operator!=(const const_iterator& lhs, const const_iterator& rhs)
      {
        return !(lhs == rhs);
      }
 
    private:
 
      typename lookup_t::const_iterator ilookup;
    };
 
    typedef ETL_OR_STD::reverse_iterator<iterator>                   reverse_iterator;
    typedef ETL_OR_STD::reverse_iterator<const_iterator>             const_reverse_iterator;
    typedef typename etl::iterator_traits<iterator>::difference_type difference_type;
 
  protected:
 
    typedef const TKey& key_parameter_t;
 
  private:
 
    //*********************************************************************
    //*********************************************************************
    class Compare
    {
    public:
 
      bool operator()(const value_type& element, const key_type& key) const
      {
        return comp(element.first, key);
      }
 
      bool operator()(const key_type& key, const value_type& element) const
      {
        return comp(key, element.first);
      }
 
#if ETL_USING_CPP11
      template <typename K, typename KC = TKeyCompare, etl::enable_if_t<comparator_is_transparent<KC>::value, int> = 0>
      bool operator()(const value_type& element, const K& key) const
      {
        return comp(element.first, key);
      }
 
      template <typename K, typename KC = TKeyCompare, etl::enable_if_t<comparator_is_transparent<KC>::value, int> = 0>
      bool operator()(const K& key, const value_type& element) const
      {
        return comp(key, element.first);
      }
#endif
 
      key_compare comp;
    };
 
  public:
 
    //*********************************************************************
    //*********************************************************************
    iterator begin()
    {
      return iterator(lookup.begin());
    }
 
    //*********************************************************************
    //*********************************************************************
    const_iterator begin() const
    {
      return const_iterator(lookup.begin());
    }
 
    //*********************************************************************
    //*********************************************************************
    iterator end()
    {
      return iterator(lookup.end());
    }
 
    //*********************************************************************
    //*********************************************************************
    const_iterator end() const
    {
      return const_iterator(lookup.end());
    }
 
    //*********************************************************************
    //*********************************************************************
    const_iterator cbegin() const
    {
      return const_iterator(lookup.cbegin());
    }
 
    //*********************************************************************
    //*********************************************************************
    const_iterator cend() const
    {
      return const_iterator(lookup.cend());
    }
 
    //*********************************************************************
    //*********************************************************************
    reverse_iterator rbegin()
    {
      return reverse_iterator(lookup.rbegin());
    }
 
    //*********************************************************************
    //*********************************************************************
    const_reverse_iterator rbegin() const
    {
      return reverse_iterator(lookup.rbegin());
    }
 
    //*********************************************************************
    //*********************************************************************
    reverse_iterator rend()
    {
      return reverse_iterator(lookup.rend());
    }
 
    //*********************************************************************
    //*********************************************************************
    const_reverse_iterator rend() const
    {
      return const_reverse_iterator(lookup.rend());
    }
 
    //*********************************************************************
    //*********************************************************************
    const_reverse_iterator crbegin() const
    {
      return const_reverse_iterator(lookup.crbegin());
    }
 
    //*********************************************************************
    //*********************************************************************
    const_reverse_iterator crend() const
    {
      return const_reverse_iterator(lookup.crend());
    }
 
    //*********************************************************************
    //*********************************************************************
    mapped_type& at(key_parameter_t key)
    {
      iterator i_element = lower_bound(key);
 
      ETL_ASSERT((i_element != end()) && keys_are_equal(i_element->first, key), ETL_ERROR(flat_map_out_of_bounds));
 
      return i_element->second;
    }
 
#if ETL_USING_CPP11
    //*********************************************************************
    template <typename K, typename KC = TKeyCompare, etl::enable_if_t<comparator_is_transparent<KC>::value, int> = 0>
    mapped_type& at(const K& key)
    {
      iterator i_element = lower_bound(key);
 
      ETL_ASSERT((i_element != end()) && keys_are_equal(i_element->first, key), ETL_ERROR(flat_map_out_of_bounds));
 
      return i_element->second;
    }
#endif
 
    //*********************************************************************
    //*********************************************************************
    const mapped_type& at(key_parameter_t key) const
    {
      const_iterator i_element = lower_bound(key);
 
      ETL_ASSERT((i_element != end()) && keys_are_equal(i_element->first, key), ETL_ERROR(flat_map_out_of_bounds));
 
      return i_element->second;
    }
 
#if ETL_USING_CPP11
    //*********************************************************************
    template <typename K, typename KC = TKeyCompare, etl::enable_if_t<comparator_is_transparent<KC>::value, int> = 0>
    const mapped_type& at(const K& key) const
    {
      const_iterator i_element = lower_bound(key);
 
      ETL_ASSERT((i_element != end()) && keys_are_equal(i_element->first, key), ETL_ERROR(flat_map_out_of_bounds));
 
      return i_element->second;
    }
#endif
 
    //*********************************************************************
    //*********************************************************************
    template <typename TIterator>
    void assign(TIterator first, TIterator last)
    {
      ETL_STATIC_ASSERT((etl::is_same<value_type, typename etl::iterator_traits< TIterator>::value_type>::value), "Incompatible data for assign");
 
#if ETL_IS_DEBUG_BUILD
      difference_type d = etl::distance(first, last);
      ETL_ASSERT(d <= difference_type(capacity()), ETL_ERROR(flat_map_full));
#endif
 
      clear();
 
      while (first != last)
      {
        insert(*first);
        ++first;
      }
    }
 
    //*********************************************************************
    //*********************************************************************
    ETL_OR_STD::pair<iterator, bool> insert(reference value)
    {
      iterator i_element = lower_bound(value.first);
 
      return insert_at(i_element, value);
    }
 
    //*********************************************************************
    //*********************************************************************
    iterator insert(const_iterator /*position*/, reference value)
    {
      return insert(value).first;
    }
 
    //*********************************************************************
    //*********************************************************************
    template <class TIterator>
    void insert(TIterator first, TIterator last)
    {
      while (first != last)
      {
        insert(*first);
        ++first;
      }
    }
 
    //*********************************************************************
    //*********************************************************************
    size_t erase(key_parameter_t key)
    {
      iterator i_element = find(key);
 
      if (i_element == end())
      {
        return 0U;
      }
      else
      {
        lookup.erase(i_element.ilookup);
        return 1U;
      }
    }
 
#if ETL_USING_CPP11
    //*********************************************************************
    template <typename K, typename KC = TKeyCompare, etl::enable_if_t<comparator_is_transparent<KC>::value, int> = 0>
    size_t erase(K&& key)
    {
      iterator i_element = find(etl::forward<K>(key));
 
      if (i_element == end())
      {
        return 0U;
      }
      else
      {
        lookup.erase(i_element.ilookup);
        return 1U;
      }
    }
#endif
 
    //*********************************************************************
    //*********************************************************************
    iterator erase(iterator i_element)
    {
      return lookup.erase(i_element.ilookup);
    }
 
    //*********************************************************************
    //*********************************************************************
    iterator erase(const_iterator i_element)
    {
      return lookup.erase(i_element.ilookup);
    }
 
    //*********************************************************************
    //*********************************************************************
    iterator erase(const_iterator first, const_iterator last)
    {
      return lookup.erase(first.ilookup, last.ilookup);
    }
 
    //*************************************************************************
    //*************************************************************************
    void clear()
    {
      lookup.clear();
    }
 
    //*********************************************************************
    //*********************************************************************
    iterator find(key_parameter_t key)
    {
      iterator itr = lower_bound(key);
 
      if (itr != end())
      {
        if (keys_are_equal(itr->first, key))
        {
          return itr;
        }
        else
        {
          return end();
        }
      }
 
      return end();
    }
 
#if ETL_USING_CPP11
    //*********************************************************************
    template <typename K, typename KC = TKeyCompare, etl::enable_if_t<comparator_is_transparent<KC>::value, int> = 0>
    iterator find(const K& key)
    {
      iterator itr = lower_bound(key);
 
      if (itr != end())
      {
        if (keys_are_equal(itr->first, key))
        {
          return itr;
        }
        else
        {
          return end();
        }
      }
 
      return end();
    }
#endif
 
    //*********************************************************************
    //*********************************************************************
    const_iterator find(key_parameter_t key) const
    {
      const_iterator itr = lower_bound(key);
 
      if (itr != end())
      {
        if (keys_are_equal(itr->first, key))
        {
          return itr;
        }
        else
        {
          return end();
        }
      }
 
      return end();
    }
 
#if ETL_USING_CPP11
    //*********************************************************************
    template <typename K, typename KC = TKeyCompare, etl::enable_if_t<comparator_is_transparent<KC>::value, int> = 0>
    const_iterator find(const K& key) const
    {
      const_iterator itr = lower_bound(key);
 
      if (itr != end())
      {
        if (keys_are_equal(itr->first, key))
        {
          return itr;
        }
        else
        {
          return end();
        }
      }
 
      return end();
    }
#endif
 
    //*********************************************************************
    //*********************************************************************
    size_t count(key_parameter_t key) const
    {
      return (find(key) == end()) ? 0U : 1U;
    }
 
#if ETL_USING_CPP11
    //*********************************************************************
    template <typename K, typename KC = TKeyCompare, etl::enable_if_t<comparator_is_transparent<KC>::value, int> = 0>
    size_t count(const K& key) const
    {
      return (find(key) == end()) ? 0U : 1U;
    }
#endif
 
    //*********************************************************************
    //*********************************************************************
    iterator lower_bound(key_parameter_t key)
    {
      return etl::lower_bound(begin(), end(), key, compare);
    }
 
#if ETL_USING_CPP11
    //*********************************************************************
    template <typename K, typename KC = TKeyCompare, etl::enable_if_t<comparator_is_transparent<KC>::value, int> = 0>
    iterator lower_bound(const K& key)
    {
      return etl::lower_bound(begin(), end(), key, compare);
    }
#endif
 
    //*********************************************************************
    //*********************************************************************
    const_iterator lower_bound(key_parameter_t key) const
    {
      return etl::lower_bound(cbegin(), cend(), key, compare);
    }
 
#if ETL_USING_CPP11
    //*********************************************************************
    template <typename K, typename KC = TKeyCompare, etl::enable_if_t<comparator_is_transparent<KC>::value, int> = 0>
    const_iterator lower_bound(const K& key) const
    {
      return etl::lower_bound(cbegin(), cend(), key, compare);
    }
#endif
 
    //*********************************************************************
    //*********************************************************************
    iterator upper_bound(key_parameter_t key)
    {
      return etl::upper_bound(begin(), end(), key, compare);
    }
 
#if ETL_USING_CPP11
    //*********************************************************************
    template <typename K, typename KC = TKeyCompare, etl::enable_if_t<comparator_is_transparent<KC>::value, int> = 0>
    iterator upper_bound(const K& key)
    {
      return etl::upper_bound(begin(), end(), key, compare);
    }
#endif
 
    //*********************************************************************
    //*********************************************************************
    const_iterator upper_bound(key_parameter_t key) const
    {
      return etl::upper_bound(begin(), end(), key, compare);
    }
 
#if ETL_USING_CPP11
    //*********************************************************************
    template <typename K, typename KC = TKeyCompare, etl::enable_if_t<comparator_is_transparent<KC>::value, int> = 0>
    const_iterator upper_bound(const K& key) const
    {
      return etl::upper_bound(begin(), end(), key, compare);
    }
#endif
 
    //*********************************************************************
    //*********************************************************************
    ETL_OR_STD::pair<iterator, iterator> equal_range(key_parameter_t key)
    {
      iterator i_lower = etl::lower_bound(begin(), end(), key, compare);
 
      return ETL_OR_STD::make_pair(i_lower, etl::upper_bound(i_lower, end(), key, compare));
    }
 
#if ETL_USING_CPP11
    //*********************************************************************
    template <typename K, typename KC = TKeyCompare, etl::enable_if_t<comparator_is_transparent<KC>::value, int> = 0>
    ETL_OR_STD::pair<iterator, iterator> equal_range(const K& key)
    {
      iterator i_lower = etl::lower_bound(begin(), end(), key, compare);
 
      return ETL_OR_STD::make_pair(i_lower, etl::upper_bound(i_lower, end(), key, compare));
    }
#endif
 
    //*********************************************************************
    //*********************************************************************
    ETL_OR_STD::pair<const_iterator, const_iterator> equal_range(key_parameter_t key) const
    {
      const_iterator i_lower = etl::lower_bound(cbegin(), cend(), key, compare);
 
      return ETL_OR_STD::make_pair(i_lower, etl::upper_bound(i_lower, cend(), key, compare));
    }
 
#if ETL_USING_CPP11
    //*********************************************************************
    template <typename K, typename KC = TKeyCompare, etl::enable_if_t<comparator_is_transparent<KC>::value, int> = 0>
    ETL_OR_STD::pair<const_iterator, const_iterator> equal_range(const K& key) const
    {
      const_iterator i_lower = etl::lower_bound(cbegin(), cend(), key, compare);
 
      return ETL_OR_STD::make_pair(i_lower, etl::upper_bound(i_lower, cend(), key, compare));
    }
#endif
 
    //*************************************************************************
    //*************************************************************************
    bool contains(const TKey& key) const
    {
      return find(key) != end();
    }
 
#if ETL_USING_CPP11
    //*************************************************************************
    template <typename K, typename KC = TKeyCompare, etl::enable_if_t<comparator_is_transparent<KC>::value, int> = 0>
    bool contains(const K& k) const
    {
      return find(k) != end();
    }
#endif
 
    //*************************************************************************
    //*************************************************************************
    size_type size() const
    {
      return lookup.size();
    }
 
    //*************************************************************************
    //*************************************************************************
    bool empty() const
    {
      return lookup.empty();
    }
 
    //*************************************************************************
    //*************************************************************************
    bool full() const
    {
      return lookup.full();
    }
 
    //*************************************************************************
    //*************************************************************************
    size_type capacity() const
    {
      return lookup.capacity();
    }
 
    //*************************************************************************
    //*************************************************************************
    size_type max_size() const
    {
      return lookup.max_size();
    }
 
    //*************************************************************************
    //*************************************************************************
    size_t available() const
    {
      return lookup.available();
    }
 
  protected:
 
    //*********************************************************************
    //*********************************************************************
    ireference_flat_map(lookup_t& lookup_)
      : lookup(lookup_)
    {
    }
 
    //*********************************************************************
    //*********************************************************************
    ETL_OR_STD::pair<iterator, bool> insert_at(iterator i_element, value_type& value)
    {
      ETL_OR_STD::pair<iterator, bool> result(end(), false);
 
      if (i_element == end())
      {
        // At the end.
        ETL_ASSERT(!lookup.full(), ETL_ERROR(flat_map_full));
 
        lookup.push_back(&value);
        result.first  = --end();
        result.second = true;
      }
      else
      {
        // Not at the end.
        result.first = i_element;
 
        // Not an existing element?
        if (!keys_are_equal(i_element->first, value.first))
        {
          // A new one.
          ETL_ASSERT(!lookup.full(), ETL_ERROR(flat_map_full));
          lookup.insert(i_element.ilookup, &value);
          result.second = true;
        }
      }
 
      return result;
    }
 
    //*********************************************************************
    //*********************************************************************
    bool keys_are_equal(key_parameter_t key1, key_parameter_t key2) const
    {
      return !key_compare()(key1, key2) && !key_compare()(key2, key1);
    }
 
#if ETL_USING_CPP11
    //*********************************************************************
    template <typename K1, typename K2, typename KC = TKeyCompare, etl::enable_if_t<comparator_is_transparent<KC>::value, int> = 0>
    bool keys_are_equal(const K1& key1, const K2& key2) const
    {
      return !key_compare()(key1, key2) && !key_compare()(key2, key1);
    }
#endif
 
  private:
 
    // Disable copy construction and assignment.
    ireference_flat_map(const ireference_flat_map&);
    ireference_flat_map& operator=(const ireference_flat_map&);
 
    lookup_t& lookup;
 
    Compare compare;
 
    //*************************************************************************
    //*************************************************************************
#if defined(ETL_POLYMORPHIC_REFERENCE_FLAT_MAP) || defined(ETL_POLYMORPHIC_CONTAINERS)
 
  public:
 
    virtual ~ireference_flat_map() {}
#else
 
  protected:
 
    ~ireference_flat_map() {}
#endif
  };
 
  //***************************************************************************
  //***************************************************************************
  template <typename TKey, typename TMapped, typename TKeyCompare>
  bool operator==(const etl::ireference_flat_map<TKey, TMapped, TKeyCompare>& lhs, const etl::ireference_flat_map<TKey, TMapped, TKeyCompare>& rhs)
  {
    return (lhs.size() == rhs.size()) && etl::equal(lhs.begin(), lhs.end(), rhs.begin());
  }
 
  //***************************************************************************
  //***************************************************************************
  template <typename TKey, typename TMapped, typename TKeyCompare>
  bool operator!=(const etl::ireference_flat_map<TKey, TMapped, TKeyCompare>& lhs, const etl::ireference_flat_map<TKey, TMapped, TKeyCompare>& rhs)
  {
    return !(lhs == rhs);
  }
 
  //***************************************************************************
  //***************************************************************************
  template <typename TKey, typename TValue, const size_t MAX_SIZE_, typename TCompare = etl::less<TKey> >
  class reference_flat_map : public ireference_flat_map<TKey, TValue, TCompare>
  {
  public:
 
    static ETL_CONSTANT size_t MAX_SIZE = MAX_SIZE_;
 
    //*************************************************************************
    //*************************************************************************
    reference_flat_map()
      : ireference_flat_map<TKey, TValue, TCompare>(lookup)
    {
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename TIterator>
    reference_flat_map(TIterator first, TIterator last)
      : ireference_flat_map<TKey, TValue, TCompare>(lookup)
    {
      ireference_flat_map<TKey, TValue, TCompare>::assign(first, last);
    }
 
    //*************************************************************************
    //*************************************************************************
    ~reference_flat_map()
    {
      ireference_flat_map<TKey, TValue, TCompare>::clear();
    }
 
    //*************************************************************************
    //*************************************************************************
    reference_flat_map& operator=(const reference_flat_map& rhs)
    {
      if (&rhs != this)
      {
        ireference_flat_map<TKey, TValue, TCompare>::assign(rhs.cbegin(), rhs.cend());
      }
 
      return *this;
    }
 
  private:
 
    reference_flat_map(const reference_flat_map&);
 
    typedef typename ireference_flat_map<TKey, TValue, TCompare>::value_type node_t;
 
    // The vector that stores pointers to the nodes.
    etl::vector<node_t*, MAX_SIZE> lookup;
  };
 
  template <typename TKey, typename TValue, const size_t MAX_SIZE_, typename TCompare>
  ETL_CONSTANT size_t reference_flat_map< TKey, TValue, MAX_SIZE_, TCompare>::MAX_SIZE;
 
  //*************************************************************************
  //*************************************************************************
#if ETL_USING_CPP17 && ETL_HAS_INITIALIZER_LIST
  template <typename... TPairs>
  reference_flat_map(TPairs...)
    -> reference_flat_map<typename etl::nth_type_t<0, TPairs...>::first_type, typename etl::nth_type_t<0, TPairs...>::second_type, sizeof...(TPairs)>;
#endif
 
  //*************************************************************************
  //*************************************************************************
#if ETL_USING_CPP11 && ETL_HAS_INITIALIZER_LIST
  template <typename TKey, typename TMapped, typename TKeyCompare = etl::less<TKey>, typename... TPairs>
  constexpr auto make_reference_flat_map(TPairs&&... pairs) -> etl::reference_flat_map<TKey, TMapped, sizeof...(TPairs), TKeyCompare>
  {
    return {etl::forward<TPairs>(pairs)...};
  }
#endif
} // namespace etl
 
#endif