    // Copyright (C) 2003  Davis E. King (davis@dlib.net)
    // License: Boost Software License   See LICENSE.txt for the full license.
    #undef DLIB_HASH_MAP_KERNEl_ABSTRACT_
    #ifdef DLIB_HASH_MAP_KERNEl_ABSTRACT_

    #include "../general_hash/general_hash.h"
    #include "../interfaces/enumerable.h"
    #include "../interfaces/remover.h"
    #include "../interfaces/map_pair.h"
    #include "../serialize.h"
    #include "../algs.h"
    #include <functional>

    namespace dlib
    {

        template <
            typename domain,
            typename range,
            unsigned long expnum,
            typename mem_manager = default_memory_manager,
            typename compare = std::less<T>
            >
        class hash_map : public enumerable<map_pair<domain,range> >,
                         public pair_remover<domain,range>
        {

            /*!
                REQUIREMENTS ON domain
                    domain must be comparable by compare where compare is a functor compatible with std::less and
                    domain must be hashable by general_hash
                    (general_hash is defined in dlib/general_hash) and
                    domain must be swappable by a global swap() and
                    domain must have a default constructor

                REQUIREMENTS ON range
                    range must be swappable by a global swap() and
                    range must have a default constructor

                REQUIREMENTS ON expnum
                    expnum < 32
                    2^expnum is the number of buckets to hash items of type T into.
                    Note that this is really just a suggestion to the hash table.
                    Implementations are free to manage the table size however is most
                    appropriate.

                REQUIREMENTS ON mem_manager
                    must be an implementation of memory_manager/memory_manager_kernel_abstract.h or
                    must be an implementation of memory_manager_global/memory_manager_global_kernel_abstract.h or
                    must be an implementation of memory_manager_stateless/memory_manager_stateless_kernel_abstract.h
                    mem_manager::type can be set to anything.

                POINTERS AND REFERENCES TO INTERNAL DATA
                    swap(), is_in_domain(), and operator[] functions do
                    not invalidate pointers or references to internal data.
                    All other functions have no such guarantees.

                INITIAL VALUE
                    size() == 0

                ENUMERATION ORDER
                    No order is specified.  Only that each element will be visited once
                    and only once.

                WHAT THIS OBJECT REPRESENTS
                    hash_map contains items of type domain and range

                    This object is similar an array.  It maps items of type domain on to
                    items of type range.

                    Also note that unless specified otherwise, no member functions
                    of this object throw exceptions.

                    definition of equivalent:
                    a is equivalent to b if
                    a < b == false and
                    b < a == false
            !*/

            public:

                typedef domain domain_type;
                typedef range range_type;
                typedef compare compare_type;
                typedef mem_manager mem_manager_type;

                hash_map(
                );
                /*!
                    ensures
                        - #*this is properly initialized
                    throws
                        - std::bad_alloc or any exception thrown by domain's or range's
                          constructor.
                !*/

                virtual ~hash_map(
                );
                /*!
                    ensures
                        - all memory associated with *this has been released
                !*/

                void clear(
                );
                /*!
                    ensures
                        - #*this has its initial value
                    throws
                        - std::bad_alloc or any exception thrown by domain's or range's
                          constructor.
                            if this exception is thrown then *this is unusable
                            until clear() is called and succeeds
                !*/

                void add (
                    domain& d,
                    range& r
                );
                /*!
                    requires
                        - &d != &r (i.e. d and r cannot be the same variable)
                        - is_in_domain(d)  == false
                    ensures
                        - #is_in_domain(d) == true
                        - #operator[](d)   == r
                        - #d and #r have initial values for their types
                        - #size() == size() + 1
                        - #at_start() == true
                    throws
                        - std::bad_alloc or any exception thrown by domain's or range's
                          constructor.
                            if add() throws then it has no effect
                !*/

                bool is_in_domain (
                    const domain& d
                ) const;
                /*!
                    ensures
                        - returns whether or not an element equivalent to d is in the
                          domain of *this
                !*/

                void remove (
                    const domain& d,
                    domain& d_copy,
                    range& r
                );
                /*!
                    requires
                        - &d != &r (i.e. d and r cannot be the same variable)
                        - &d != &d_copy (i.e. d and d_copy cannot be the same variable)
                        - &r != &d_copy (i.e. r and d_copy cannot be the same variable)
                        - is_in_domain(d) == true
                    ensures
                        - #is_in_domain(d) == false
                        - #d_copy is equivalent to d
                        - the element in the range of *this associated with #d_copy has
                          been swapped into #r
                        - #size() == size() - 1
                        - #at_start() == true
                !*/

                void destroy (
                    const domain& d
                );
                /*!
                    requires
                        - is_in_domain(d) == true
                    ensures
                        - #is_in_domain(d) == false
                        - #size() == size() - 1
                        - #at_start() == true
                !*/

                range& operator[] (
                    const domain& d
                );
                /*!
                    requires
                        - is_in_domain(d) == true
                    ensures
                        - returns a non-const reference to the element in the range of *this
                          associated with the element equivalent to d
                !*/

                const range& operator[] (
                    const domain& d
                ) const;
                /*!
                    requires
                        - is_in_domain(d) == true
                    ensures
                        - returns a const reference to the element in the range of *this
                          associated with the element equivalent to d
                !*/

                void swap (
                    hash_map& item
                );
                /*!
                    ensures
                        - swaps *this and item
                !*/

            private:

                // restricted functions
                hash_map(hash_map&);
                hash_map& operator=(hash_map&);
        };

        template <
            typename domain,
            typename range,
            unsigned long expnum,
            typename mem_manager,
            typename compare
            >
        inline void swap (
            hash_map<domain,range,expnum,mem_manager,compare>& a,
            hash_map<domain,range,expnum,mem_manager,compare>& b
        ) { a.swap(b); }
        /*!
            provides a global swap function
        !*/

        template <
            typename domain,
            typename range,
            unsigned long expnum,
            typename mem_manager,
            typename compare
            >
        void deserialize (
            hash_map<domain,range,expnum,mem_manager,compare>& item,
            std::istream& in
        );
        /*!
            provides deserialization support
        !*/
    }

    #endif // DLIB_HASH_MAP_KERNEl_ABSTRACT_