# File lib/rgl/base.rb, line 124
124:     def each_edge (&block)
125:       if directed?
126:         each_vertex { |u|
127:           each_adjacent(u) { |v| yield u,v }
128:         }
129:       else
130:         each_edge_aux(&block)       # concrete graphs should to this better
131:       end
132:     end