-- File graphg.ads
--  This is a generic graph package with an active iterator. The package
--  will be used in a larger program that performs graph traversals using
--  the iterator (lab6). For this purpose the iterator is not sufficient,
--  in that the *iterator* marks nodes as visited when they are returned. 
--  This makes it impossible to correctly perform depth-first traversals.
--  The flaws will be fixed in a subsequent version that students
--  implement as a child package of this package.

generic

   type Element is private;

package Graphg is

   type Graph (Size: positive) is limited private;

   type Iterator is private;

-- constructors

   procedure Clear (AGraph: in out Graph);

   procedure Add (ANode: in positive;
                  WithValue: in Element;
                  ToGraph: in out Graph);

   procedure InsertEdge (FromNode: in positive; 
                         ToNode: in positive;
                         InGraph: in out Graph);

-- iterator operations

   procedure Initialize (AnIterator: out Iterator;
                         ForGraph: in out Graph;
                         ToNode: in positive);

   procedure GetNext (IteratorNode: in out Iterator;
                      ForGraph: in out Graph);

   function ValueOf (IteratorNode: in Iterator;
                     ForGraph: in Graph) return Element;

   function Done (IteratorNode: in Iterator;
                  ForGraph: in Graph) return Boolean;
     -- return True if all nodes adjacent to that specified by
     -- IteratorNode have been visited

-- hidden part

private

   type Iterator is new Positive;
   type GoodNode is array (positive range <>) of Boolean;
   type Nodes is array (positive range <>) of Element;
   type AdjMatrix is array (positive range <>, positive range <>) 
      of Boolean;
   type Graph (Size: positive) is
      record
         InGraph: GoodNode (1..Size);
         Visited: GoodNode (1..Size);
         Values: Nodes (1..Size);
         Edges: AdjMatrix (1..Size, 1..Size);
      end record;

end graphg;