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module Enumerable
# Produces an array of arrays of all possible combinations
# of the given arrays in the position given. (Explain me better?)
#
# 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
# _____ _
# |_ _|__ ___| |_
# | |/ _ \/ __| __|
# | | __/\__ \ |_
# |_|\___||___/\__|
#
=begin test
require 'test/unit'
class TCEnumerable < Test::Unit::TestCase
def test_combinations
a = [1,2]
b = [3,4]
r = Enumerable.combinations(a,b)
assert_equal( [[1,3],[1,4],[2,3],[2,4]], r )
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 = Enumerable.combinations(a, b, c)
assert_equal( r, z )
end
end
=end
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19 entries across 19 versions & 1 rubygems