flatten an array of arbitrarily nested arrays of integers into a flat array of integers

flatflat.rb

class Array
  def flatflat
    result = []
    self.each do |elem|
      if elem.is_a?(Array)
        result.concat(elem.flatflat)
      else
        result.push(elem)
      end
    end
    result
  end
end

require 'test/unit'

class ArrayTest < Test::Unit::TestCase

  def test_flatflat
    arr = [[[]],[],[],[],[]]
    assert_equal( [], arr.flatflat )
    arr = [1, 2, 3, [[4,5,]], 6, 7, [8,9], 10, 11, [12]]
    assert_equal( [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12], arr.flatflat )
  end
  
end

require 'benchmark'

ARRAY = 10000.times.map { |i| rand(10000) }

ITERATIONS = 10000

Benchmark.bm do |benchmark|

  puts "#{ITERATIONS} iterations"

  benchmark.report("Array.flatten") do
    ITERATIONS.times { |i| ARRAY.flatten }
  end

  benchmark.report("Array.flatflat") do
    ITERATIONS.times { |i| ARRAY.flatflat }
  end

end