recursive reverse.rb

require 'test/unit'

class TestRecursiveReverse < Test::Unit::TestCase

  def test_o_make
    assert_equal [3, 2, 1], RecursiveReverse.new.o_make([1, 2, 3])
  end

  def test_f_make
    assert_equal [3, 2, 1], RecursiveReverse.new.f_make([1, 2, 3])
  end

end

class RecursiveReverse

  def o_make(array)
    @ts ||= array.size

    if @ts.zero?
      array
    else
      @ts -= 1
      array.insert(@ts, array.shift)
      o_make(array)
    end
  end

  def f_make(array)
    if array.empty?
      array
    else
      f_make(array[1..-1]) + [array.first]
    end
  end

end