A recursive partition method for Ruby's String.

recursive_partition.rb

class String
  def recursive_partition(sep)
    result = self.partition(sep)
    if sep != "" && result[2].match(sep)
      extra = result.pop
      result << extra.recursive_partition(sep)
    end
    result.flatten
  end
end

recursive_partition_test.rb

require 'test/unit'
require './recursive_partition.rb'

class RecursivePartitionTest < Test::Unit::TestCase
  TEST_STR = "status=active,status=pending;start_date>=2011-01-01;end_date<2011-02-01"

  def test_no_match_with_regex
    result = TEST_STR.recursive_partition(/<=/)
    assert_equal(result, [TEST_STR, "", ""])
  end

  def test_no_match_with_string
    result = TEST_STR.recursive_partition("<=")
    assert_equal(result, [TEST_STR, "", ""])
  end

  def test_single_match_with_regex
    result = TEST_STR.recursive_partition(/>=/)
    assert_equal(result, ["status=active,status=pending;start_date", ">=", "2011-01-01;end_date<2011-02-01"])
  end

  def test_single_match_with_string
    result = TEST_STR.recursive_partition(">=")
    assert_equal(result, ["status=active,status=pending;start_date", ">=", "2011-01-01;end_date<2011-02-01"])
  end

  def test_two_matches_with_regex
    result = TEST_STR.recursive_partition(/;/)
    assert_equal(result, ["status=active,status=pending", ";", "start_date>=2011-01-01", ";", "end_date<2011-02-01"])
  end

  def test_two_matches_with_string
    result = TEST_STR.recursive_partition(";")
    assert_equal(result, ["status=active,status=pending", ";", "start_date>=2011-01-01", ";", "end_date<2011-02-01"])
  end

  def test_multiple_matches_with_regex
    result = TEST_STR.recursive_partition(/\=/)
    assert_equal(result, ["status", "=", "active,status", "=", "pending;start_date>", "=", "2011-01-01;end_date<2011-02-01"])
  end

  def test_multiple_matches_with_string
    result = TEST_STR.recursive_partition("=")
    assert_equal(result, ["status", "=", "active,status", "=", "pending;start_date>", "=", "2011-01-01;end_date<2011-02-01"])
  end

  def test_with_blank_separator
    result = TEST_STR.recursive_partition("")
    assert_equal(result, ["", "", TEST_STR])
  end
  
  def test_with_blank_string
    result = "".recursive_partition("")
    assert_equal(result, ["", "", ""])
  end

end