text: /**
   * MIT License
   * 
   * Copyright (c) 2017 Tessil
   * 
   * Permission is hereby granted, free of charge, to any person obtaining a copy
   * of this software and associated documentation files (the "Software"), to deal
   * in the Software without restriction, including without limitation the rights
   * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   * copies of the Software, and to permit persons to whom the Software is
   * furnished to do so, subject to the following conditions:
   * 
   * The above copyright notice and this permission notice shall be included in all
   * copies or substantial portions of the Software.
   * 
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
   * SOFTWARE.
   */
  #ifndef TSL_SPARSE_MAP_H
  #define TSL_SPARSE_MAP_H 
  
  
  #include <cstddef>
  #include <functional>
  #include <initializer_list>
  #include <memory>
  #include <type_traits>
  #include <utility>
  #include "sparse_hash.h"
  
  
  namespace tsl {
  
      
  /**
   * Implementation of a sparse hash map using open-addressing with quadratic probing.
   * The goal on the hash map is to be the most memory efficient possible, even at low load factor,
   * while keeping reasonable performances.
   * 
   * `GrowthPolicy` defines how the map grows and consequently how a hash value is mapped to a bucket. 
   * By default the map uses `tsl::sh::power_of_two_growth_policy`. This policy keeps the number of buckets 
   * to a power of two and uses a mask to map the hash to a bucket instead of the slow modulo.
   * Other growth policies are available and you may define your own growth policy, 
   * check `tsl::sh::power_of_two_growth_policy` for the interface.
   * 
   * `ExceptionSafety` defines the exception guarantee provided by the class. By default only the basic
   * exception safety is guaranteed which mean that all resources used by the hash map will be freed (no memory leaks) 
   * but the hash map may end-up in an undefined state if an exception is thrown (undefined here means that some elements  
   * may be missing). This can ONLY happen on rehash (either on insert or if `rehash` is called explicitly) and will
   * occur if the Allocator can't allocate memory (`std::bad_alloc`) or if the copy constructor (when a nothrow 
   * move constructor is not available) throws and exception. This can be avoided by calling `reserve` beforehand.
   * This basic guarantee is similar to the one of `google::sparse_hash_map` and `spp::sparse_hash_map`.
   * It is possible to ask for the strong exception guarantee with `tsl::sh::exception_safety::strong`, the drawback
   * is that the map will be slower on rehashes and will also need more memory on rehashes.
   * 
   * `Sparsity` defines how much the hash set will compromise between insertion speed and memory usage. A high
   * sparsity means less memory but longer insertion times, and vice-versa for low sparsity. The default 
   * tsl::sh::sparsity::medium sparsity offers a good compromise. It doesn't change the lookups speed.
   * 
   * If the destructor of `Key` or `T` throws an exception, the behaviour of the class is undefined.
   * 
   * Iterators invalidation:
   *  - clear, operator=, reserve, rehash: always invalidate the iterators.
   *  - insert, emplace, emplace_hint, operator[]: if there is an effective insert, invalidate the iterators.
   *  - erase: always invalidate the iterators.
   */
  template<class Key, 
           class T, 
           class Hash = std::hash<Key>,
           class KeyEqual = std::equal_to<Key>,
           class Allocator = std::allocator<std::pair<Key, T>>,
           class GrowthPolicy = tsl::sh::power_of_two_growth_policy<2>,
           tsl::sh::exception_safety ExceptionSafety = tsl::sh::exception_safety::basic,
           tsl::sh::sparsity Sparsity = tsl::sh::sparsity::medium>
  class sparse_map {
  private:
      template<typename U>
      using has_is_transparent = tsl::detail_sparse_hash::has_is_transparent<U>;
      
      class KeySelect {
      public:
          using key_type = Key;
          
          const key_type& operator()(const std::pair<Key, T>& key_value) const noexcept {
              return key_value.first;
          }
          
          key_type& operator()(std::pair<Key, T>& key_value) noexcept {
              return key_value.first;
          }
      };  
      
      class ValueSelect {
      public:
          using value_type = T;
          
          const value_type& operator()(const std::pair<Key, T>& key_value) const noexcept {
              return key_value.second;
          }
          
          value_type& operator()(std::pair<Key, T>& key_value) noexcept {
              return key_value.second;
          }
      };
      
      using ht = detail_sparse_hash::sparse_hash<std::pair<Key, T>, KeySelect, ValueSelect,
                                                 Hash, KeyEqual, Allocator, GrowthPolicy,
                                                 ExceptionSafety, Sparsity,
                                                 tsl::sh::probing::quadratic>;  
                                               
  public:
      using key_type = typename ht::key_type;
      using mapped_type = T;
      using value_type = typename ht::value_type;
      using size_type = typename ht::size_type;
      using difference_type = typename ht::difference_type;
      using hasher = typename ht::hasher;
      using key_equal = typename ht::key_equal;
      using allocator_type = typename ht::allocator_type;
      using reference = typename ht::reference;
      using const_reference = typename ht::const_reference;
      using pointer = typename ht::pointer;
      using const_pointer = typename ht::const_pointer;
      using iterator = typename ht::iterator;
      using const_iterator = typename ht::const_iterator;
      
      
  public:
      /*
       * Constructors
       */
      sparse_map(): sparse_map(ht::DEFAULT_INIT_BUCKETS_SIZE) {
      }
      
      explicit sparse_map(size_type bucket_count, 
                          const Hash& hash = Hash(),
                          const KeyEqual& equal = KeyEqual(),
                          const Allocator& alloc = Allocator()): 
                      m_ht(bucket_count, hash, equal, alloc, ht::DEFAULT_MAX_LOAD_FACTOR)
      {
      }
      
      sparse_map(size_type bucket_count,
                 const Allocator& alloc): sparse_map(bucket_count, Hash(), KeyEqual(), alloc)
      {
      }
      
      sparse_map(size_type bucket_count,
                 const Hash& hash,
                 const Allocator& alloc): sparse_map(bucket_count, hash, KeyEqual(), alloc)
      {
      }
      
      explicit sparse_map(const Allocator& alloc): sparse_map(ht::DEFAULT_INIT_BUCKETS_SIZE, alloc) {
      }
      
      template<class InputIt>
      sparse_map(InputIt first, InputIt last,
                 size_type bucket_count = ht::DEFAULT_INIT_BUCKETS_SIZE,
                 const Hash& hash = Hash(),
                 const KeyEqual& equal = KeyEqual(),
                 const Allocator& alloc = Allocator()): sparse_map(bucket_count, hash, equal, alloc)
      {
          insert(first, last);
      }
      
      template<class InputIt>
      sparse_map(InputIt first, InputIt last,
                 size_type bucket_count,
                 const Allocator& alloc): sparse_map(first, last, bucket_count, Hash(), KeyEqual(), alloc)
      {
      }
      
      template<class InputIt>
      sparse_map(InputIt first, InputIt last,
                 size_type bucket_count,
                 const Hash& hash,
                 const Allocator& alloc): sparse_map(first, last, bucket_count, hash, KeyEqual(), alloc)
      {
      }
  
      sparse_map(std::initializer_list<value_type> init,
                 size_type bucket_count = ht::DEFAULT_INIT_BUCKETS_SIZE,
                 const Hash& hash = Hash(),
                 const KeyEqual& equal = KeyEqual(),
                 const Allocator& alloc = Allocator()): 
            sparse_map(init.begin(), init.end(), bucket_count, hash, equal, alloc)
      {
      }
  
      sparse_map(std::initializer_list<value_type> init,
                 size_type bucket_count,
                 const Allocator& alloc): 
            sparse_map(init.begin(), init.end(), bucket_count, Hash(), KeyEqual(), alloc)
      {
      }
  
      sparse_map(std::initializer_list<value_type> init,
                 size_type bucket_count,
                 const Hash& hash,
                 const Allocator& alloc): 
            sparse_map(init.begin(), init.end(), bucket_count, hash, KeyEqual(), alloc)
      {
      }
      
      sparse_map& operator=(std::initializer_list<value_type> ilist) {
          m_ht.clear();
          
          m_ht.reserve(ilist.size());
          m_ht.insert(ilist.begin(), ilist.end());
          
          return *this;
      }
      
      allocator_type get_allocator() const { return m_ht.get_allocator(); }
      
      
      /*
       * Iterators
       */
      iterator begin() noexcept { return m_ht.begin(); }
      const_iterator begin() const noexcept { return m_ht.begin(); }
      const_iterator cbegin() const noexcept { return m_ht.cbegin(); }
      
      iterator end() noexcept { return m_ht.end(); }
      const_iterator end() const noexcept { return m_ht.end(); }
      const_iterator cend() const noexcept { return m_ht.cend(); }
      
      
      /*
       * Capacity
       */
      bool empty() const noexcept { return m_ht.empty(); }
      size_type size() const noexcept { return m_ht.size(); }
      size_type max_size() const noexcept { return m_ht.max_size(); }
      
      /*
       * Modifiers
       */
      void clear() noexcept { m_ht.clear(); }
      
      
      
      std::pair<iterator, bool> insert(const value_type& value) { 
          return m_ht.insert(value); 
      }
          
      template<class P, typename std::enable_if<std::is_constructible<value_type, P&&>::value>::type* = nullptr>
      std::pair<iterator, bool> insert(P&& value) { 
          return m_ht.emplace(std::forward<P>(value)); 
      }
      
      std::pair<iterator, bool> insert(value_type&& value) { 
          return m_ht.insert(std::move(value)); 
      }
      
      
      iterator insert(const_iterator hint, const value_type& value) { 
          return m_ht.insert(hint, value); 
      }
          
      template<class P, typename std::enable_if<std::is_constructible<value_type, P&&>::value>::type* = nullptr>
      iterator insert(const_iterator hint, P&& value) { 
          return m_ht.emplace_hint(hint, std::forward<P>(value));
      }
      
      iterator insert(const_iterator hint, value_type&& value) { 
          return m_ht.insert(hint, std::move(value)); 
      }
      
      
      template<class InputIt>
      void insert(InputIt first, InputIt last) { 
          m_ht.insert(first, last); 
      }
      
      void insert(std::initializer_list<value_type> ilist) { 
          m_ht.insert(ilist.begin(), ilist.end()); 
      }
  
      
      
      
      template<class M>
      std::pair<iterator, bool> insert_or_assign(const key_type& k, M&& obj) { 
          return m_ht.insert_or_assign(k, std::forward<M>(obj)); 
      }
  
      template<class M>
      std::pair<iterator, bool> insert_or_assign(key_type&& k, M&& obj) { 
          return m_ht.insert_or_assign(std::move(k), std::forward<M>(obj)); 
      }
      
      template<class M>
      iterator insert_or_assign(const_iterator hint, const key_type& k, M&& obj) {
          return m_ht.insert_or_assign(hint, k, std::forward<M>(obj));
      }
      
      template<class M>
      iterator insert_or_assign(const_iterator hint, key_type&& k, M&& obj) {
          return m_ht.insert_or_assign(hint, std::move(k), std::forward<M>(obj));
      }
      
      
      
      /**
       * Due to the way elements are stored, emplace will need to move or copy the key-value once.
       * The method is equivalent to insert(value_type(std::forward<Args>(args)...));
       * 
       * Mainly here for compatibility with the std::unordered_map interface.
       */
      template<class... Args>
      std::pair<iterator, bool> emplace(Args&&... args) { 
          return m_ht.emplace(std::forward<Args>(args)...); 
      }
      
      
      
      /**
       * Due to the way elements are stored, emplace_hint will need to move or copy the key-value once.
       * The method is equivalent to insert(hint, value_type(std::forward<Args>(args)...));
       * 
       * Mainly here for compatibility with the std::unordered_map interface.
       */
      template<class... Args>
      iterator emplace_hint(const_iterator hint, Args&&... args) {
          return m_ht.emplace_hint(hint, std::forward<Args>(args)...);
      }
      
      
      
      
      template<class... Args>
      std::pair<iterator, bool> try_emplace(const key_type& k, Args&&... args) { 
          return m_ht.try_emplace(k, std::forward<Args>(args)...);
      }
      
      template<class... Args>
      std::pair<iterator, bool> try_emplace(key_type&& k, Args&&... args) {
          return m_ht.try_emplace(std::move(k), std::forward<Args>(args)...);
      }
      
      template<class... Args>
      iterator try_emplace(const_iterator hint, const key_type& k, Args&&... args) {
          return m_ht.try_emplace(hint, k, std::forward<Args>(args)...);
      }
      
      template<class... Args>
      iterator try_emplace(const_iterator hint, key_type&& k, Args&&... args) {
          return m_ht.try_emplace(hint, std::move(k), std::forward<Args>(args)...);
      }
      
      
  
      
      iterator erase(iterator pos) { return m_ht.erase(pos); }
      iterator erase(const_iterator pos) { return m_ht.erase(pos); }
      iterator erase(const_iterator first, const_iterator last) { return m_ht.erase(first, last); }
      size_type erase(const key_type& key) { return m_ht.erase(key); }
      
      /**
       * Use the hash value 'precalculated_hash' instead of hashing the key. The hash value should be the same
       * as hash_function()(key). Usefull to speed-up the lookup to the value if you already have the hash.
       */    
      size_type erase(const key_type& key, std::size_t precalculated_hash) { 
          return m_ht.erase(key, precalculated_hash); 
      }
      
      /**
       * This overload only participates in the overload resolution if the typedef KeyEqual::is_transparent exists. 
       * If so, K must be hashable and comparable to Key.
       */
      template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr> 
      size_type erase(const K& key) { return m_ht.erase(key); }
      
      /**
       * @copydoc erase(const K& key)
       * 
       * Use the hash value 'precalculated_hash' instead of hashing the key. The hash value should be the same
       * as hash_function()(key). Usefull to speed-up the lookup to the value if you already have the hash.
       */    
      template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr> 
      size_type erase(const K& key, std::size_t precalculated_hash) { 
          return m_ht.erase(key, precalculated_hash); 
      }
      
      
      
      void swap(sparse_map& other) { other.m_ht.swap(m_ht); }
      
      
      
      /*
       * Lookup
       */
      T& at(const Key& key) { return m_ht.at(key); }
      
      /**
       * Use the hash value 'precalculated_hash' instead of hashing the key. The hash value should be the same
       * as hash_function()(key). Usefull to speed-up the lookup if you already have the hash.
       */
      T& at(const Key& key, std::size_t precalculated_hash) { return m_ht.at(key, precalculated_hash); }
      
      
      const T& at(const Key& key) const { return m_ht.at(key); }
      
      /**
       * @copydoc at(const Key& key, std::size_t precalculated_hash)
       */
      const T& at(const Key& key, std::size_t precalculated_hash) const { return m_ht.at(key, precalculated_hash); }
      
      
      /**
       * This overload only participates in the overload resolution if the typedef KeyEqual::is_transparent exists. 
       * If so, K must be hashable and comparable to Key.
       */
      template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr> 
      T& at(const K& key) { return m_ht.at(key); }
  
      /**
       * @copydoc at(const K& key)
       * 
       * Use the hash value 'precalculated_hash' instead of hashing the key. The hash value should be the same
       * as hash_function()(key). Usefull to speed-up the lookup if you already have the hash.
       */    
      template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr> 
      T& at(const K& key, std::size_t precalculated_hash) { return m_ht.at(key, precalculated_hash); }
      
      
      /**
       * @copydoc at(const K& key)
       */
      template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr> 
      const T& at(const K& key) const { return m_ht.at(key); }
      
      /**
       * @copydoc at(const K& key, std::size_t precalculated_hash)
       */    
      template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr> 
      const T& at(const K& key, std::size_t precalculated_hash) const { return m_ht.at(key, precalculated_hash); }
      
      
      
      
      T& operator[](const Key& key) { return m_ht[key]; }    
      T& operator[](Key&& key) { return m_ht[std::move(key)]; }
      
      
      
      
      size_type count(const Key& key) const { return m_ht.count(key); }
      
      /**
       * Use the hash value 'precalculated_hash' instead of hashing the key. The hash value should be the same
       * as hash_function()(key). Usefull to speed-up the lookup if you already have the hash.
       */
      size_type count(const Key& key, std::size_t precalculated_hash) const { 
          return m_ht.count(key, precalculated_hash); 
      }
      
      /**
       * This overload only participates in the overload resolution if the typedef KeyEqual::is_transparent exists. 
       * If so, K must be hashable and comparable to Key.
       */
      template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr> 
      size_type count(const K& key) const { return m_ht.count(key); }
      
      /**
       * @copydoc count(const K& key) const
       * 
       * Use the hash value 'precalculated_hash' instead of hashing the key. The hash value should be the same
       * as hash_function()(key). Usefull to speed-up the lookup if you already have the hash.
       */     
      template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr> 
      size_type count(const K& key, std::size_t precalculated_hash) const { return m_ht.count(key, precalculated_hash); }
      
      
      
      
      iterator find(const Key& key) { return m_ht.find(key); }
      
      /**
       * Use the hash value 'precalculated_hash' instead of hashing the key. The hash value should be the same
       * as hash_function()(key). Usefull to speed-up the lookup if you already have the hash.
       */
      iterator find(const Key& key, std::size_t precalculated_hash) { return m_ht.find(key, precalculated_hash); }
      
      const_iterator find(const Key& key) const { return m_ht.find(key); }
      
      /**
       * @copydoc find(const Key& key, std::size_t precalculated_hash)
       */
      const_iterator find(const Key& key, std::size_t precalculated_hash) const { 
          return m_ht.find(key, precalculated_hash); 
      }
      
      /**
       * This overload only participates in the overload resolution if the typedef KeyEqual::is_transparent exists. 
       * If so, K must be hashable and comparable to Key.
       */
      template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr> 
      iterator find(const K& key) { return m_ht.find(key); }
      
      /**
       * @copydoc find(const K& key)
       * 
       * Use the hash value 'precalculated_hash' instead of hashing the key. The hash value should be the same
       * as hash_function()(key). Usefull to speed-up the lookup if you already have the hash.
       */
      template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr> 
      iterator find(const K& key, std::size_t precalculated_hash) { return m_ht.find(key, precalculated_hash); }
      
      /**
       * @copydoc find(const K& key)
       */
      template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr> 
      const_iterator find(const K& key) const { return m_ht.find(key); }
      
      /**
       * @copydoc find(const K& key)
       * 
       * Use the hash value 'precalculated_hash' instead of hashing the key. The hash value should be the same
       * as hash_function()(key). Usefull to speed-up the lookup if you already have the hash.
       */
      template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr> 
      const_iterator find(const K& key, std::size_t precalculated_hash) const { 
          return m_ht.find(key, precalculated_hash); 
      }
      
      
      
      
      std::pair<iterator, iterator> equal_range(const Key& key) { return m_ht.equal_range(key); }
      
      /**
       * Use the hash value 'precalculated_hash' instead of hashing the key. The hash value should be the same
       * as hash_function()(key). Usefull to speed-up the lookup if you already have the hash.
       */
      std::pair<iterator, iterator> equal_range(const Key& key, std::size_t precalculated_hash) { 
          return m_ht.equal_range(key, precalculated_hash); 
      }
      
      std::pair<const_iterator, const_iterator> equal_range(const Key& key) const { return m_ht.equal_range(key); }
      
      /**
       * @copydoc equal_range(const Key& key, std::size_t precalculated_hash)
       */
      std::pair<const_iterator, const_iterator> equal_range(const Key& key, std::size_t precalculated_hash) const { 
          return m_ht.equal_range(key, precalculated_hash); 
      }
  
      /**
       * This overload only participates in the overload resolution if the typedef KeyEqual::is_transparent exists. 
       * If so, K must be hashable and comparable to Key.
       */
      template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr> 
      std::pair<iterator, iterator> equal_range(const K& key) { return m_ht.equal_range(key); }
      
      
      /**
       * @copydoc equal_range(const K& key)
       * 
       * Use the hash value 'precalculated_hash' instead of hashing the key. The hash value should be the same
       * as hash_function()(key). Usefull to speed-up the lookup if you already have the hash.
       */
      template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr> 
      std::pair<iterator, iterator> equal_range(const K& key, std::size_t precalculated_hash) { 
          return m_ht.equal_range(key, precalculated_hash); 
      }
      
      /**
       * @copydoc equal_range(const K& key)
       */
      template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr> 
      std::pair<const_iterator, const_iterator> equal_range(const K& key) const { return m_ht.equal_range(key); }
      
      /**
       * @copydoc equal_range(const K& key, std::size_t precalculated_hash)
       */    
      template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr> 
      std::pair<const_iterator, const_iterator> equal_range(const K& key, std::size_t precalculated_hash) const { 
          return m_ht.equal_range(key, precalculated_hash); 
      }
      
      
      
      
      /*
       * Bucket interface 
       */
      size_type bucket_count() const { return m_ht.bucket_count(); }
      size_type max_bucket_count() const { return m_ht.max_bucket_count(); }
      
      
      /*
       *  Hash policy 
       */
      float load_factor() const { return m_ht.load_factor(); }
      float max_load_factor() const { return m_ht.max_load_factor(); }
      void max_load_factor(float ml) { m_ht.max_load_factor(ml); }
      
      void rehash(size_type count) { m_ht.rehash(count); }
      void reserve(size_type count) { m_ht.reserve(count); }
      
      
      /*
       * Observers
       */
      hasher hash_function() const { return m_ht.hash_function(); }
      key_equal key_eq() const { return m_ht.key_eq(); }
      
      /*
       * Other
       */
      
      /**
       * Convert a const_iterator to an iterator.
       */
      iterator mutable_iterator(const_iterator pos) {
          return m_ht.mutable_iterator(pos);
      }
      
      friend bool operator==(const sparse_map& lhs, const sparse_map& rhs) {
          if(lhs.size() != rhs.size()) {
              return false;
          }
          
          for(const auto& element_lhs: lhs) {
              const auto it_element_rhs = rhs.find(element_lhs.first);
              if(it_element_rhs == rhs.cend() || element_lhs.second != it_element_rhs->second) {
                  return false;
              }
          }
          
          return true;
      }
  
      friend bool operator!=(const sparse_map& lhs, const sparse_map& rhs) {
          return !operator==(lhs, rhs);
      }
  
      friend void swap(sparse_map& lhs, sparse_map& rhs) {
          lhs.swap(rhs);
      }
      
  private:
      ht m_ht;
  };
  
  
  /**
   * Same as `tsl::sparse_map<Key, T, Hash, KeyEqual, Allocator, tsl::sh::prime_growth_policy>`.
   */
  template<class Key, 
           class T, 
           class Hash = std::hash<Key>,
           class KeyEqual = std::equal_to<Key>,
           class Allocator = std::allocator<std::pair<Key, T>>>
  using sparse_pg_map = sparse_map<Key, T, Hash, KeyEqual, Allocator, tsl::sh::prime_growth_policy>;
  
  } // end namespace tsl
  
  #endif
  