+
+ # Connects two vertices, creating and storing a new edge
+ # Also adds the vertices, unless they're already in the graph
+ def connect(vertex1, vertex2)
+ self.vertices << vertex1 unless self.vertices.include? vertex1
+ self.vertices << vertex2 unless self.vertices.include? vertex2
+ edge = Edge.new
+ self.edges << edge
+ edge << vertex1 << vertex2
+ end
+
+ # Form a product graph of this graph and the other.
+ # Return the new graph.
+ def product(other)
+ product_graph = Graph.new
+ self.vertices.each do |v1|
+ other.vertices.each do |v2|
+ product_graph << Vertex.new({:g1_vertex => v1, :g2_vertex => v2})
+ end
+ end
+ self.edges.each do |e1|
+ e1_vertices = e1.vertices
+ other.edges.each do |e2|
+ e2_vertices = e2.vertices
+ source = product_graph.vertices.find {|v| v.g1_vertex == e1_vertices[0] and v.g2_vertex == e2_vertices[0]}
+ destination = product_graph.vertices.find {|v| v.g1_vertex == e1_vertices[1] and v.g2_vertex == e2_vertices[1]}
+ product_graph.connect source, destination
+ source = product_graph.vertices.find {|v| v.g1_vertex == e1_vertices[0] and v.g2_vertex == e2_vertices[1]}
+ destination = product_graph.vertices.find {|v| v.g1_vertex == e1_vertices[1] and v.g2_vertex == e2_vertices[0]}
+ product_graph.connect source, destination
+ end
+ end
+ product_graph
+ end
+
+ end # class