lib/graph.njae/edge.rb

   1 # A simple graph library
   2
   3 module GraphNjae
   4
   5   # An edge (or multiedge) in a graph. The edge can have arbitrary attributes,
   6   # treated as method names.
   7   #
   8   # Each connection is handled by a Graph::Connection object, so that each end
   9   # of the Edge can have it's own attributes.
  10   class Edge < OpenStruct
  11     def initialize(values = {})
  12       super(values)
  13       self.connections = []
  14       self
  15     end
  16
  17     # Connect this edge to a vertex
  18     def <<(other)
  19       c = Connection.new
  20       c.end = other
  21       other.edges << self unless other.edges.include? self
  22       self.connections << c
  23       self
  24     end
  25
  26     # Return the set of vertices this edge connects.
  27     def vertices
  28       self.connections.map {|c| c.end}
  29     end
  30
  31     # Return the connection object that joins this Edge to the specified Vertex
  32     def connection_at(vertex)
  33       self.connections.find {|c| c.end.equal?  vertex}
  34     end
  35
  36     # Return the vertex at the other end of the one given.
  37     # Self-loops should still return the vertex
  38     def other_end(vertex)
  39       if self.vertices[0] == vertex
  40         self.vertices[1]
  41       else
  42         self.vertices[0]
  43       end
  44     end
  45
  46     def to_s
  47       '<E: ' + self.type.to_s + ' [' + self.vertices.map {|n| n.to_s}.join(', ') + '] >'
  48     end
  49
  50     def to_dot(opts = {})
  51       if block_given?
  52         yield self
  53       else
  54         dot = self.connections[0].end.object_id.to_s + " -- " + self.connections[1].end.object_id.to_s
  55         if opts.size > 0
  56           dot << ' {'
  57           dot << opts.keys.map { |k|
  58             (k.to_s + ' = "' + self.instance_eval(opts[k].to_s).to_s) + '"'
  59                         }.join(', ')
  60           dot << '}'
  61         end
  62         dot << ';'
  63       end
  64     end
  65
  66   end
  67
  68   # A connection between an Edge and a Vertex.The connection can have arbitrary attributes,
  69   # treated as method names.
  70   class Connection < OpenStruct
  71     def initialize(values = {})
  72       super(values)
  73       self
  74     end
  75   end
  76 end