-----------------------------------------------------------------------------
-- PACKAGE:
--      List_Sets
-- AUTHOR:
--      Yoav Tzruya
-- EXPORTED TYPES:
--      Set - derived from absrtact_sets.set -  a set implemented by
--      a dynamic list and controlled by finailize and adjust
-- EXPORTED PROCEDURES:
--      (see abstract_sets.ads)
-- EXPORTED EXCEPTIONS:
--      (see abstract_sets.ads)
-----------------------------------------------------------------------------
-- ** SPECIFICATION IMPORTS **
with Abstract_Sets;

generic
        type Set_Element is private;
       
        -- a function to convert one element to a string
        with function to_string (
                        element_arg : in     set_element )
             return string;

        -- an abstract set of elements
        with package abstract_set_handling is new
               abstract_sets(set_element=> set_element,to_string=> to_string);

package List_Sets is


        -- ** EXPORTED EXCEPTIONS **

        set_is_empty_exception : exception renames abstract_set_handling.set_is_empty_exception;

        -- ** EXPORTED TYPES **
      
        type Set is new Abstract_Set_Handling.set with private;

        -- ** EXPORTED SUBPROGRAMS **


        function Empty
                return Set;
                -- empty set

        function Unit (
                        Element : in     Set_Element)
                return Set;
                -- build set with 1 element

        function Union (
                        Left  : in    Set;
                        Right : in    Set)
                return Set;

        function Intersection (
                        Left  : in    Set;
                        Right : in    Set)
                return Set;

        procedure Take (
                        From    : in out Set;
                        Element :    out Set_Element);
                -- may raise the following exceptions :
                -- o set_is_empty_exception
        
        function to_String (
                        Set_arg : in    Set)
                 return String;

private
        procedure Adjust     (Object : in out Set);
        procedure Finalize   (Object : in out Set);

        type node;
        type access_node is access node;
        type node is
             record
                 next : access_node := null;
                 elem : set_element;
             end record;

        type Set is
                new Abstract_Set_Handling.Set with
                record
                        head : access_node;
                end record;
                        
end List_Sets;