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Nanoc3::DirectedGraph

Represents a directed graph. It is used by the dependency tracker for storing and querying dependencies between items.

@example Creating and using a directed graph

# Create a graph with three vertices
graph = DirectedGraph.new(%w( a b c d ))

# Add edges
graph.add_edge('a', 'b')
graph.add_edge('b', 'c')
graph.add_edge('c', 'd')

# Get (direct) predecessors
graph.direct_predecessors_of('d').sort
  # => %w( c )
graph.predecessors_of('d').sort
  # => %w( a b c )

# Modify edges
graph.remove_edge('a', 'b')

# Get (direct) predecessors again
graph.direct_predecessors_of('d').sort
  # => %w( c )
graph.predecessors_of('d').sort
  # => %w( b c )

Attributes

vertices[R]

The list of vertices in this graph.

@return [Array]

Public Class Methods

new(vertices) click to toggle source

Creates a new directed graph with the given vertices.

# File lib/nanoc3/base/directed_graph.rb, line 41
def initialize(vertices)
  @vertices = vertices

  @from_graph = {}
  @to_graph   = {}

  @vertice_indexes = {}
  vertices.each_with_index do |v, i|
    @vertice_indexes[v] = i
  end

  invalidate_caches
end

Public Instance Methods

add_edge(from, to) click to toggle source

Adds an edge from the first vertex to the second vertex.

@param from Vertex where the edge should start @param to Vertex where the edge should end

@return [void]

# File lib/nanoc3/base/directed_graph.rb, line 61
def add_edge(from, to)
  @from_graph[from] ||= Set.new
  @from_graph[from] << to

  @to_graph[to] ||= Set.new
  @to_graph[to]  << from

  invalidate_caches
end
delete_edges_to(to) click to toggle source

Deletes all edges going to the given vertex.

@param to Vertex to which all edges should be removed

@return [void]

# File lib/nanoc3/base/directed_graph.rb, line 93
def delete_edges_to(to)
  @to_graph[to] ||= Set.new
  @to_graph[to].each do |from|
    @from_graph[from].delete(to)
  end
  @to_graph.delete(to)
end
direct_predecessors_of(to) click to toggle source

Returns the direct predecessors of the given vertex, i.e. the vertices x where there is an edge from x to the given vertex y.

@param to The vertex of which the predecessors should be calculated

@return [Array] Direct predecessors of the given vertex

# File lib/nanoc3/base/directed_graph.rb, line 107
def direct_predecessors_of(to)
  @to_graph[to].to_a
end
direct_successors_of(from) click to toggle source

Returns the direct successors of the given vertex, i.e. the vertices y where there is an edge from the given vertex x to y.

@param from The vertex of which the successors should be calculated

@return [Array] Direct successors of the given vertex

# File lib/nanoc3/base/directed_graph.rb, line 117
def direct_successors_of(from)
  @from_graph[from].to_a
end
edges() click to toggle source

Returns an array of tuples representing the edges. The result of this method may take a while to compute and should be cached if possible.

@return [Array] The list of all edges in this graph.

# File lib/nanoc3/base/directed_graph.rb, line 145
def edges
  result = []
  @vertices.each_with_index do |v, i|
    direct_successors_of(v).map { |v2| @vertice_indexes[v2] }.each do |i2|
      result << [ i, i2 ]
    end
  end
  result
end
predecessors_of(to) click to toggle source

Returns the predecessors of the given vertex, i.e. the vertices x for which there is a path from x to the given vertex y.

@param to The vertex of which the predecessors should be calculated

@return [Array] Predecessors of the given vertex

# File lib/nanoc3/base/directed_graph.rb, line 127
def predecessors_of(to)
  @predecessors[to] ||= recursively_find_vertices(to, :direct_predecessors_of)
end
remove_edge(from, to) click to toggle source

Removes the edge from the first vertex to the second vertex. If the edge does not exist, nothing is done.

@param from Start vertex of the edge @param to End vertex of the edge

@return [void]

# File lib/nanoc3/base/directed_graph.rb, line 78
def remove_edge(from, to)
  @from_graph[from] ||= Set.new
  @from_graph[from].delete(to)

  @to_graph[to] ||= Set.new
  @to_graph[to].delete(from)

  invalidate_caches
end
successors_of(from) click to toggle source

Returns the successors of the given vertex, i.e. the vertices y for which there is a path from the given vertex x to y.

@param from The vertex of which the successors should be calculated

@return [Array] Successors of the given vertex

# File lib/nanoc3/base/directed_graph.rb, line 137
def successors_of(from)
  @successors[from] ||= recursively_find_vertices(from, :direct_successors_of)
end

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