Module: Plexus::AdjacencyGraphBuilder

Included in:
AdjacencyGraph
Defined in:
lib/plexus/adjacency_graph.rb

Overview

This module provides the basic routines needed to implement the specialized builders: DigraphBuilder, UndirectedGraphBuilder, DirectedPseudoGraphBuilder, UndirectedPseudoGraphBuilder, DirectedMultiGraphBuilder and UndirectedMultiGraphBuilder modules, each of them streamlining AdjacencyGraphBuilder's behavior. Those implementations rely on the GraphBuilder.

Defined Under Namespace

Classes: ArrayWithAdd

Instance Method Summary collapse

Instance Method Details

#add_edge!(arc) ⇒ AdjacencyGraph #add_edge!(source, target, label = nil) ⇒ AdjacencyGraph

Adds an edge to the graph.

Can be called in two basic ways, label is optional:

Overloads:


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# File 'lib/plexus/adjacency_graph.rb', line 109

def add_edge!(u, v = nil, l = nil, n = nil)
  n = u.number if u.class.include? ArcNumber and n.nil?
  u, v, l = u.source, u.target, u.label if u.is_a? Plexus::Arc

  return self if !@allow_loops && u == v

  n = (@next_edge_number += 1) unless n if @parallel_edges
  add_vertex!(u)
  add_vertex!(v)
  @vertex_dict[u].add(v)
  (@edge_number[u] ||= @edgelist_class.new).add(n) if @parallel_edges

  unless directed?
    @vertex_dict[v].add(u)
    (@edge_number[v] ||= @edgelist_class.new).add(n) if @parallel_edges
  end

  self[n ? edge_class[u,v,n] : edge_class[u,v]] = l if l
  self
end

#add_vertex!(vertex, label = nil) ⇒ Object

Adds a vertex to the graph with an optional label.

Parameters:

  • vertex (vertex(Object))

    any kind of Object can act as a vertex

  • label (#to_s) (defaults to: nil)

    (nil)


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# File 'lib/plexus/adjacency_graph.rb', line 87

def add_vertex!(vertex, label = nil)
  @vertex_dict[vertex] ||= @edgelist_class.new
  self[vertex] = label if label
  self
end

#adjacent(x, options = {}) ⇒ Object

FIXME, EFFED UP (but why?)


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# File 'lib/plexus/adjacency_graph.rb', line 209

def adjacent(x, options = {})
  options[:direction] ||= :out

  if !x.is_a?(Plexus::Arc) and (options[:direction] == :out || !directed?)
    if options[:type] == :edges
      i = -1
      @parallel_edges ?
        @vertex_dict[x].map { |v| e = edge_class[x, v, @edge_number[x][i+=1]]; e.label = self[e]; e } :
        @vertex_dict[x].map { |v| e = edge_class[x, v];  e.label = self[e]; e }
    else
      @vertex_dict[x].to_a
    end
  else
    graph_adjacent(x,options)
  end
end

#edge?(u, v = nil) ⇒ Boolean

Returns true if [u,v] or u is an Plexus::Arc (an “O(1)” implementation of `edge?`).

Parameters:

  • u (vertex)
  • v (vertex) (defaults to: nil)

    (nil)

Returns:

  • (Boolean)

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# File 'lib/plexus/adjacency_graph.rb', line 78

def edge?(u, v = nil)
  u, v = u.source, u.target if u.is_a? Plexus::Arc
  vertex?(u) and @vertex_dict[u].include?(v)
end

#edgesArray

Returns an array of edges, most likely of class Plexus::Arc or Edge depending upon the type of graph.

Returns:

  • (Array)

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# File 'lib/plexus/adjacency_graph.rb', line 190

def edges
  @vertex_dict.keys.inject(Set.new) do |a,v|
    if @parallel_edges and @edge_number[v]
      @vertex_dict[v].zip(@edge_number[v]).each do |w|
        s, t, n = v, w[0], w[1]
        a.add(edge_class[s, t, n, edge_label(s, t, n)])
      end
    else
      @vertex_dict[v].each do |w|
        a.add(edge_class[v, w, edge_label(v, w)])
      end
    end
    a
  end.to_a
end

#implementation_initialize(*params) ⇒ Object

This method is called by the specialized implementations upon graph creation.

Initialization parameters can include:

  • an array of edges to add

  • one or several graphs to copy (will be merged if multiple)

  • `:parallel_edges` denotes that duplicate edges are allowed

  • `:loops denotes` that loops are allowed

Parameters:

  • *params (Hash)

    the initialization parameters


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# File 'lib/plexus/adjacency_graph.rb', line 27

def implementation_initialize(*params)
  @vertex_dict = Hash.new
  clear_all_labels

  # FIXME: could definitely make use of the activesupport helper
  # extract_options! and facets' reverse_merge! technique
  # to handle parameters
  args = (params.pop if params.last.is_a? Hash) || {}

  # Basic configuration of adjacency.
  @allow_loops    = args[:loops]          || false
  @parallel_edges = args[:parallel_edges] || false
  @edgelist_class = @parallel_edges ? ArrayWithAdd : Set
  if @parallel_edges
    @edge_number      = Hash.new
    @next_edge_number = 0
  end

  # Copy any given graph into this graph.
  params.select { |p| p.is_a? Plexus::GraphBuilder }.each do |g|
    g.edges.each do |e|
      add_edge!(e)
      edge_label_set(e, edge_label(e)) if edge_label(e)
    end
    g.vertices.each do |v|
      add_vertex!(v)
      vertex_label_set(v, vertex_label(v)) if vertex_label(v)
    end
  end

  # Add all array edges specified.
  params.select { |p| p.is_a? Array }.each do |a|
    0.step(a.size-1, 2) { |i| add_edge!(a[i], a[i+1]) }
  end
end

#remove_edge!(a) ⇒ AdjacencyGraph #remove_edge!(u, v) ⇒ AdjacencyGraph

Removes an edge from the graph.

Can be called with both source and target as vertex, or with source and object of Plexus::Arc derivation.

Overloads:

Raises:

  • (ArgumentError)

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# File 'lib/plexus/adjacency_graph.rb', line 160

def remove_edge!(u, v = nil)
  unless u.is_a? Plexus::Arc
    raise ArgumentError if @parallel_edges
    u = edge_class[u,v]
  end
  raise ArgumentError if @parallel_edges and (u.number || 0) == 0
  return self unless @vertex_dict[u.source] # It doesn't exist
  delete_label(u) # Get rid of label
  if @parallel_edges
    index = @edge_number[u.source].index(u.number)
    raise NoArcError unless index
    @vertex_dict[u.source].delete_at(index)
    @edge_number[u.source].delete_at(index)
  else
    @vertex_dict[u.source].delete(u.target)
  end
  self
end

#remove_vertex!(v) ⇒ AdjacencyGraph

Removes a given vertex from the graph.

Parameters:

  • v (vertex)

Returns:


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# File 'lib/plexus/adjacency_graph.rb', line 134

def remove_vertex!(v)
  # FIXME This is broken for multi graphs
  @vertex_dict.delete(v)
  @vertex_dict.each_value { |adjList| adjList.delete(v) }
  @vertex_dict.keys.each do |u|
    delete_label(edge_class[u,v])
    delete_label(edge_class[v,u])
  end
  delete_label(v)
  self
end

#vertex?(v) ⇒ Boolean

Returns true if v is a vertex of this Graph (an “O(1)” implementation of `vertex?`).

Parameters:

  • v (vertex)

Returns:

  • (Boolean)

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# File 'lib/plexus/adjacency_graph.rb', line 68

def vertex?(v)
  @vertex_dict.has_key?(v)
end

#verticesArray

Returns an array of vertices that the graph has.

Returns:

  • (Array)

    graph's vertices


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# File 'lib/plexus/adjacency_graph.rb', line 182

def vertices
  @vertex_dict.keys
end