class Sass::Script::Parser

def unary(op, sub)
  class_eval <<RUBY
    def unary_#{op}
      return #{sub} unless tok = try_tok(:#{op})
      interp = try_op_before_interp(tok) and return interp
      line = @lexer.line 
      op = UnaryOperation.new(assert_expr(:unary_#{op}), :#{op})
      op.line = line
      op
    end
end