Contents

class Array

  # Produces an array of arrays of all possible combinations 
  # of the given arrays in the position given. (Explain me better?)
  #
  #   require 'facet/arrat/combinations'
  #
  #   a = %w|a b|
  #   b = %w|a x|
  #   c = %w|x y|
  #   Array.combinations(a, b, c).each { |x| p x }
  #
  # produces
  #
  #   ["a", "a", "x"]
  #   ["a", "a", "y"]
  #   ["a", "x", "x"]
  #   ["a", "x", "y"]
  #   ["b", "a", "x"]
  #   ["b", "a", "y"]
  #   ["b", "x", "x"]
  #   ["b", "x", "y"]
  #
  def self.combinations(head, *rest)
    crest = rest.empty? ? [[]] : combinations(*rest)
    head.inject([]) { |combs, item| combs + crest.map { |comb| [item] + comb } }
  end
  
end



#__TEST__

if $0 == __FILE__
  require 'test/unit'

  class TestCase < Test::Unit::TestCase
    r = [ ["a", "a", "x"],
          ["a", "a", "y"],
          ["a", "x", "x"],
          ["a", "x", "y"],
          ["b", "a", "x"],
          ["b", "a", "y"],
          ["b", "x", "x"],
          ["b", "x", "y"] ]
    a = %w|a b|
    b = %w|a x|
    c = %w|x y|
    z = Array.combinations(a, b, c)
    assert_equal( r, z )
  end  
end

Version data entries

3 entries across 3 versions & 1 rubygems

Version	Path
facets-0.7.0	lib/facet/array/combinations.rb
facets-0.7.1	lib/facet/array/combinations.rb
facets-0.7.2	lib/facet/array/combinations.rb