Class: Nanoc3::DirectedGraph

Inherits:
Object
  • Object
show all
Defined in:
lib/nanoc3/base/directed_graph.rb

Overview

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

Examples:

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 )

Instance Attribute Summary (collapse)

Instance Method Summary (collapse)

Constructor Details

- (DirectedGraph) initialize(vertices)

Creates a new directed graph with the given vertices.



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# File 'lib/nanoc3/base/directed_graph.rb', line 42

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

Instance Attribute Details

- (Array) vertices (readonly)

The list of vertices in this graph.

Returns:



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# File 'lib/nanoc3/base/directed_graph.rb', line 39

def vertices
  @vertices
end

Instance Method Details

- (void) add_edge(from, to)

This method returns an undefined value.

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

Parameters:

  • from —

    Vertex where the edge should start

  • to —

    Vertex where the edge should end



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# File 'lib/nanoc3/base/directed_graph.rb', line 62

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

- (void) delete_edges_to(to)

This method returns an undefined value.

Deletes all edges going to the given vertex.

Parameters:

  • to —

    Vertex to which all edges should be removed



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# File 'lib/nanoc3/base/directed_graph.rb', line 94

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

- (Array) direct_predecessors_of(to)

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.

Parameters:

  • to —

    The vertex of which the predecessors should be calculated

Returns:

  • (Array) —

    Direct predecessors of the given vertex



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# File 'lib/nanoc3/base/directed_graph.rb', line 108

def direct_predecessors_of(to)
  @to_graph[to].to_a
end

- (Array) direct_successors_of(from)

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.

Parameters:

  • from —

    The vertex of which the successors should be calculated

Returns:

  • (Array) —

    Direct successors of the given vertex



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# File 'lib/nanoc3/base/directed_graph.rb', line 118

def direct_successors_of(from)
  @from_graph[from].to_a
end

- (Array) edges

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.

Returns:

  • (Array) —

    The list of all edges in this graph.



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# File 'lib/nanoc3/base/directed_graph.rb', line 146

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

- (Array) predecessors_of(to)

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.

Parameters:

  • to —

    The vertex of which the predecessors should be calculated

Returns:

  • (Array) —

    Predecessors of the given vertex



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# File 'lib/nanoc3/base/directed_graph.rb', line 128

def predecessors_of(to)
  @predecessors[to] ||= recursively_find_vertices(to, :direct_predecessors_of)
end

- (void) remove_edge(from, to)

This method returns an undefined value.

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

Parameters:

  • from —

    Start vertex of the edge

  • to —

    End vertex of the edge



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# File 'lib/nanoc3/base/directed_graph.rb', line 79

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

- (Array) successors_of(from)

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.

Parameters:

  • from —

    The vertex of which the successors should be calculated

Returns:

  • (Array) —

    Successors of the given vertex



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# File 'lib/nanoc3/base/directed_graph.rb', line 138

def successors_of(from)
  @successors[from] ||= recursively_find_vertices(from, :direct_successors_of)
end