The RGLFold module adds the fold, fold_right, compile_fold, and compile_fold_right methods to RGL graphs. Fold iterates or recurses over a graph from a given vertex, combining successive vertices using a given block. These methods work on both cyclic and acyclic graphs.

Create a directed adjacency graph and add fold functionality:

require 'rgl/adjacency'
require 'rgl-fold'
dg = RGL::DirectedAdjacencyGraph[1,2, 2,3, 2,4, 4,5, 6,4, 1,6]
dg.extend RGLFold

Return a set of every path in the graph from the root vertex:

dg.fold(1, []) {|accum, vertex| accum + [vertex]}
  #=> #<Set: {[1, 2, 3], [1, 2, 4, 5], [1, 6, 4, 5]}>

Return a set of every path in the graph from the 6 vertex:

dg.fold(6, []) {|accum, vertex| accum + [vertex]}
  #=> #<Set: {[6, 4, 5]}>

Sum the vertices for each path:

dg.fold(1, 0) {|accum, vertex| accum + vertex}
  #=> #<Set: {6, 12, 16}>

Compile and call a lambda which, when given an initial value and a fold block, returns a set of every path in the graph from the root vertex:

fold_proc = dg.compile_fold 1
fold_proc.call [] {|accum, vertex| accum + [vertex]}
  #=> #<Set: {[1, 2, 3], [1, 2, 4, 5], [1, 6, 4, 5]}>

• Check out the latest master to make sure the feature hasn’t been implemented or the bug hasn’t been fixed yet

• Check out the issue tracker to make sure someone already hasn’t requested it and/or contributed it

• Fork the project

• Start a feature/bugfix branch

• Commit and push until you are happy with your contribution

• Make sure to add tests for it. This is important so I don’t break it in a future version unintentionally.

• Please try not to mess with the Rakefile, version, or history. If you want to have your own version, or is otherwise necessary, that is fine, but please isolate to its own commit so I can cherry-pick around it.

Copyright © 2011 Joshua B. Griffith. See LICENSE.txt for further details.