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

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

    namespace dlib
    {

        template <
            typename domain,
            typename range,
            typename mem_manager = default_memory_manager,
            typename compare = std::less<domain>
            >
        class binary_search_tree : public enumerable<map_pair<domain,range> >,
                                   public asc_pair_remover<domain,range,compare>
        {

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

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

                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(), count(), height(),  and operator[] functions
                    do not invalidate pointers or references to internal data.

                    position_enumerator() invalidates pointers or references to
                    data returned by element() and only by element() (i.e. pointers and
                    references returned by operator[] are still valid).

                    All other functions have no such guarantees.

                INITIAL VALUE
                    size() == 0
                    height() == 0

                ENUMERATION ORDER
                    The enumerator will iterate over the domain (and each associated
                    range element) elements in ascending order according to the compare functor.
                    (i.e. the elements are enumerated in sorted order)

                WHAT THIS OBJECT REPRESENTS
                    this object represents a data dictionary that is built on top of some
                    kind of binary search tree.  It maps objects of type domain to objects
                    of type range.

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

                    NOTE:
                        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;

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

            virtual ~binary_search_tree(
            );
            /*!
                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
            !*/

            short height (
            ) const;
            /*!
                ensures
                    - returns the number of elements in the longest path from the root
                      of the tree to a leaf
            !*/

            unsigned long count (
                const domain& d
            ) const;
            /*!
                ensures
                    - returns the number of elements in the domain of *this that are
                      equivalent to d
            !*/

            void add (
                domain& d,
                range& r
            );
            /*!
                requires
                    - &d != &r (i.e. d and r cannot be the same variable)
                ensures
                    - adds a mapping between d and r to *this
                    - if (count(d) == 0) then
                        - #*(*this)[d] == r
                    - else
                        - #(*this)[d] != 0
                    - #d and #r have initial values for their types
                    - #count(d) == count(d) + 1
                    - #at_start() == true
                    - #size() == size() + 1
                throws
                    - std::bad_alloc or any exception thrown by domain's or range's
                      constructor.
                        if add() throws then it has no effect
            !*/

            void remove (
                const domain& d,
                domain& d_copy,
                range& r
            );
            /*!
                requires
                    - (*this)[d] != 0
                    - &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)
                ensures
                    - some element in the domain of *this that is equivalent to d has
                      been removed and swapped into #d_copy.  Additionally, its
                      associated range element has been removed and swapped into #r.
                    - #count(d) == count(d) - 1
                    - #size() == size() - 1
                    - #at_start() == true
            !*/

            void destroy (
                const domain& d
            );
            /*!
                requires
                    - (*this)[d] != 0
                ensures
                    - an element in the domain of *this equivalent to d has been removed.
                      The element in the range of *this associated with d has also been
                      removed.
                    - #count(d) == count(d) - 1
                    - #size() == size() - 1
                    - #at_start() == true
            !*/

            void remove_last_in_order (
                domain& d,
                range& r
            );
            /*!
                requires
                    - size() > 0
                ensures
                    - the last/biggest (according to the compare functor) element in the domain of *this has
                      been removed and swapped into #d.  The element in the range of *this
                      associated with #d has also been removed and swapped into #r.
                    - #count(#d) == count(#d) - 1
                    - #size() == size() - 1
                    - #at_start() == true
            !*/

            void remove_current_element (
                domain& d,
                range& r
            );
            /*!
                requires
                    - current_element_valid() == true
                ensures
                    - the current element given by element() has been removed and swapped into d and r.
                    - #d == element().key()
                    - #r == element().value()
                    - #count(#d) == count(#d) - 1
                    - #size() == size() - 1
                    - moves the enumerator to the next element.  If element() was the last
                      element in enumeration order then #current_element_valid() == false
                      and #at_start() == false.
            !*/

            void position_enumerator (
                const domain& d
            ) const;
            /*!
                ensures
                    - #at_start() == false
                    - if (count(d) > 0) then
                        - #element().key() == d
                    - else if (there are any items in the domain of *this that are bigger than
                      d according to the compare functor) then
                        - #element().key() == the smallest item in the domain of *this that is
                          bigger than d according to the compare functor.
                    - else
                        - #current_element_valid() == false
            !*/

            const range* operator[] (
                const domain& d
            ) const;
            /*!
                ensures
                    - if (there is an element in the domain equivalent to d) then
                        - returns a pointer to an element in the range of *this that
                          is associated with an element in the domain of *this
                          equivalent to d.
                    - else
                        - returns 0
            !*/

            range* operator[] (
                const domain& d
            );
            /*!
                ensures
                    - if (there is an element in the domain equivalent to d) then
                        - returns a pointer to an element in the range of *this that
                          is associated with an element in the domain of *this
                          equivalent to d.
                    - else
                        - returns 0
            !*/

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

        private:

            // restricted functions
            binary_search_tree(binary_search_tree&);
            binary_search_tree& operator=(binary_search_tree&);

        };

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

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

    #endif // DLIB_BINARY_SEARCH_TREE_KERNEl_ABSTRACT_