# File lib/rgl/traversal.rb, line 100
100:     def attach_distance_map (map = Hash.new(0))
101:       @dist_map = map
102: 
103:       class << self
104: 
105:         def handle_tree_edge (u, v)
106:           super
107:           @dist_map[v] = @dist_map[u] + 1
108:         end
109: 
110:         # Answer the distance to the start vertex.
111: 
112:         def distance_to_root (v)
113:           @dist_map[v]
114:         end
115: 
116:       end       # class
117:     end