class Regexp::Expression::Subexpression

def to_s(format = :full)
  s = ''
  # Note: the format does not get passed down to subexpressions.
  case format
  when :base
    s << @text.dup
    s << @expressions.map{|e| e.to_s}.join unless @expressions.empty?
  else
    s << @text.dup
    s << @expressions.map{|e| e.to_s}.join unless @expressions.empty?
    s << @quantifier if quantified?
  end
  s
end