lib/graph.njae/edge.rb

   1 require 'ostruct'
   2
   3 # A simple graph library
   4
   5 module GraphNjae
   6
   7   # An edge (or multiedge) in a graph. The edge can have arbitrary attributes,
   8   # treated as method names.
   9   #
  10   # Each connection is handled by a Graph::Connection object, so that each end
  11   # of the Edge can have it's own attributes.
  12   class Edge < OpenStruct
  13     def initialize(values = {})
  14       super(values)
  15       self.connections = []
  16       self
  17     end
  18
  19     # Connect this edge to a vertex
  20     def <<(other)
  21       c = Connection.new
  22       c.end = other
  23       other.edges << self unless other.edges.include? self
  24       self.connections << c
  25       self
  26     end
  27
  28     # Return the set of vertices this edge connects.
  29     def vertices
  30       self.connections.map {|c| c.end}
  31     end
  32
  33     # Return the connection object that joins this Edge to the specified Vertex
  34     def connection_at(vertex)
  35       self.connections.find {|c| c.end.equal?  vertex}
  36     end
  37
  38     # Return the vertex at the other end of the one given.
  39     # Self-loops should still return the vertex
  40     def other_end(vertex)
  41       if self.vertices[0] == vertex
  42         self.vertices[1]
  43       else
  44         self.vertices[0]
  45       end
  46     end
  47
  48     def to_s
  49       '<E: ' + self.type.to_s + ' [' + self.vertices.map {|n| n.to_s}.join(', ') + '] >'
  50     end
  51   end
  52
  53   # A connection between an Edge and a Vertex.The connection can have arbitrary attributes,
  54   # treated as method names.
  55   class Connection < OpenStruct
  56     def initialize(values = {})
  57       super(values)
  58       self
  59     end
  60   end
  61 end