class GBN_IEDGE_ITERATOR
  -- produces edgges of an indexed graph
  -- if undirected, the first copy of each
  -- edge is produced, not the second.

inherit
  GBN_ITERATOR [ GBN_IEDGE ]

creation {GBN_IGRAPH}
  make

feature {NONE}

  make ( container: like source ) is
    require
      nonvoid: container /= Void
    do
      source := container
      cursor := 1
      if not finished then
        container . logon
      end
    ensure
      valid_source: source = container
      protection: finished or else source . is_protected
    end

 feature { GBN_IGRAPH }

   source : GBN_IGRAPH
  
 feature {ANY} 

  finished: BOOLEAN is
    do
       Result := not cursor.in_range ( 1, source.the_edges.count )
    end

  forth is
    do
      cursor := cursor + 1
      if source . is_undirected then
        from
	until
	  finished or else source . the_inverses . item (cursor)
	  	> cursor
        loop
	  cursor := cursor + 1
	end
      end

      if finished then
	source.logoff
      end
    end

  stop is
    do
      cursor := source.the_edges.count + 1
      source . logoff
    end

  item : GBN_IEDGE is
    do
      Result := source . the_edges . item ( cursor )
    end
    

feature {NONE}
  cursor : INTEGER

end -- class GBN_IEDGE_ITERATOR