class Sass::Script::Tree::Operation

def to_sass(opts = {})
  o1 = operand_to_sass @operand1, :left, opts
  o2 = operand_to_sass @operand2, :right, opts
  sep =
    case @operator
    when :comma; ", "
    when :space; " "
    else; " #{Sass::Script::Lexer::OPERATORS_REVERSE[@operator]} "
    end
  "#{o1}#{sep}#{o2}"
end