class Test::Unit::Diff::SequenceMatcher

def update_to_indexes
  @to_indexes = {}
  @junks = {}
  if @to.is_a?(String)
    each = " "[0].is_a?(Integer) ? :each_byte : :each_char
  else
    each = :each
  end
  i = 0
  @to.__send__(each) do |item|
    @to_indexes[item] ||= []
    @to_indexes[item] << i
    i += 1
  end
  return if @junk_predicate.nil?
  @to_indexes = @to_indexes.reject do |key, value|
    junk = @junk_predicate.call(key)
    @junks[key] = true if junk
    junk
  end
end