-- File:	PCollection_HSet.cdl
-- Created:	Mon Sep 2 14:45:39 1991
-- Author:	Mireille MERCIEN
--		<apc@topsn1>
---Copyright:	 Matra Datavision 1991



generic class HSet from PCollection (Item as Storable) 
inherits Persistent

     ---Purpose: A set is an unordered collection of items.
     -- We can not have duplicated items in a given set.
    
raises   NoSuchObject from Standard


    class SetNode instantiates HSingleList from PCollection(Item); 

    class SetIterator from PCollection 				      
        ---Purpose: Iterator of the Set class.

    raises NoMoreObject from Standard,
           NoSuchObject from Standard
    is     
 
     	Create(S : HSet from PCollection) 
        returns SetIterator from PCollection;
        ---Purpose: Creates an iterator on the set S.
        -- Set the iterator at the beginning of the set S.

     	More(me) returns Boolean from Standard;
        ---Level: Public
        ---Purpose: Returns True if there are other items.

     	Next(me: in out) raises NoMoreObject from Standard;
        ---Level: Public
	---Purpose: Sets the iterator to the next item.
	    	
     	Value(me) returns any Item raises NoSuchObject from Standard;
        ---Level: Public
	---Purpose: Returns the item value corresponding to 
	-- the current position of the iterator.

    fields
    	 TheIterator : SetNode;
    end;


is

     Create returns mutable HSet from PCollection;
        ---Purpose: Creation of an empty set.

     Extent(me) returns Integer from Standard;
        ---Level: Public
        ---Purpose: Number of items in the set me
        ---Example: if S is the set {a,b,c,d,e} 
        -- Extent returns 5

     Last(me) returns SetNode;
        ---Level: Public
        ---Purpose: Returns the field TheLast .
        -- (the last item enterred in the set)

     IsEmpty(me) returns Boolean from Standard;
        ---Level: Public
        ---Purpose: Returns True if the set me is empty.

     Clear(me : mutable);
        ---Level: Public
	---Purpose: Removes all the items of the set me.
        ---Example: before
        --   me = {a,b,c,d}
        -- after
        --   me = {}

     Add(me : mutable; T : Item) returns Boolean from Standard;
        ---Level: Public
	---Purpose: Adds an item T in the set me if it does not already exist.
	-- Returns False if the item T already exists, True otherwise. 
        ---Example: before
        --   me = {a,b,c,d}, T = y
        -- after
        --   me = {a,b,c,d,y}

     Remove(me : mutable; T : Item) raises NoSuchObject from Standard;
        ---Level: Public
        ---Purpose: Removes the item T in the set me
        -- Raises an exception if the item is not in the set.
        ---Example: before
        --   me = {a,b,c,d}, T = a
        -- after
        --   me = {b,c,d}
        -- returns ()
 
     Union(me; B : HSet from PCollection) returns mutable HSet from PCollection;
        ---Level: Public
        ---Purpose: Creation of a set containing all the items 
        -- of the set me and all the items of the set B which 
        -- are not in me.
        ---Example: before
        --   me = {a,b,c}, B = {d,a,f}
        -- after
        --   me = {a,b,c}, B = {d,a,f}
        -- returns
        -- {a,b,c,d,f}

     Intersection(me; B : HSet from PCollection) returns mutable HSet from PCollection;
        ---Level: Public
        ---Purpose: Creation of a set containing all the 
        -- items which are both in the set <me> and in the set B.
        ---Example: before
        --   me = {a,b,c}, B = {d,a,f}
        -- after
        --   me = {a,b,c}, B = {d,a,f}
        -- returns
        --   {a}

     Difference(me; B: HSet from PCollection) returns mutable HSet from PCollection;
        ---Level: Public
        ---Purpose: Creation of a set containing the items 
        -- which are in the set me and not in the set B.
        ---Example: before
        --   me = {a,b,c}, B = {d,a,f}
        -- after
        --   me = {a,b,c}, B = {d,a,f}
        -- returns
        --   {b,c}

     Contains(me; T : Item) returns Boolean from Standard;
        ---Level: Public
        ---Purpose: Returns True if an item is in the set me.

     IsASubset(me; S : HSet from PCollection) returns Boolean from Standard;
        ---Level: Public
        ---Purpose: Returns True if a set is contained in the set me.
        -- The two sets can be identical.

     IsAProperSubset(me; S : HSet from PCollection) returns Boolean from 
        Standard;
        ---Level: Public
        ---Purpose: Returns True if a set is contained in the set me.
        -- The two sets cannot be identical.

     ShallowCopy(me) 
        returns mutable like me 
        is redefined;
        ---Level: Advanced
	---C++: function call


     ShallowDump (me; s: in out OStream) 
        is redefined;
        ---Level: Advanced
    	---C++: function call



fields
     TheExtent   : Integer from Standard;
     TheLast     : SetNode;
end;