class SassC::Script::Value::List

def to_s(opts = {})
  if !bracketed && value.empty?
    raise SassC::SyntaxError.new("#{inspect} isn't a valid CSS value.")
  end
  members = value.
    reject {|e| e.is_a?(Null) || e.is_a?(List) && e.value.empty?}.
    map {|e| e.to_s(opts)}
  contents = members.join(sep_str)
  bracketed ? "[#{contents}]" : contents
end