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Contents
#--
# Cross product adapted from code by Michael Neuman.
#++
require 'generator'
module Enumerable
# Provides the cross-product of two or more Enumerables.
# This is the class-level method. The instance method
# calls on this.
#
# Enumerable.cross([1,2], [4], ["apple", "banana"])
# #=> [[1, 4, "apple"], [1, 4, "banana"], [2, 4, "apple"], [2, 4, "banana"]]
#
# Enumerable.cross([1,2], [3,4])
# #=> [[1, 3], [1, 4], [2, 3], [2, 4]]
#
#--
# TODO Make a more efficient version just for Array (?)
#++
def self.cross(*enums, &block)
raise if enums.empty?
gens = enums.map{|e| Generator.new(e)}
return [] if gens.any? {|g| g.end?}
sz = gens.size
res = []
tuple = Array.new(sz)
loop do
# fill tuple
(0 ... sz).each { |i|
tuple[i] = gens[i].current
}
if block.nil?
res << tuple.dup
else
block.call(tuple.dup)
end
# step forward
gens[-1].next
(sz-1).downto(0) do |i|
if gens[i].end?
if i > 0
gens[i].rewind
gens[i-1].next
else
return res
end
end
end
end #loop
end
end
# _____ _
# |_ _|__ ___| |_
# | |/ _ \/ __| __|
# | | __/\__ \ |_
# |_|\___||___/\__|
#
=begin test
require 'test/unit'
class TCEnumerable < Test::Unit::TestCase
def test_cross
i = [[1,2], [3,4]]
o = [[1, 3], [1, 4], [2, 3], [2, 4]]
assert_equal( o, Enumerable.cross(*i) )
i = [[1,2], [4], ["apple", "banana"]]
o = [[1, 4, "apple"], [1, 4, "banana"], [2, 4, "apple"], [2, 4, "banana"]]
assert_equal( o, Enumerable.cross(*i) )
end
end
=end
Version data entries
11 entries across 11 versions & 1 rubygems