class Calculator
  def initialize(*args)
    @num_ary = []; @oper_ary = []
    args.each do |arg|
      arg.is_a?(Numeric) ? @num_ary << arg : @oper_ary << arg
    end
  end

  def calculate
    result = nil
    @oper_ary.each do |oper|
      num1 = result.nil? ? @num_ary.shift : result
      num2 = @num_ary.shift
      result = num1.send(oper, num2)
    end
    result
  end
end

# Calculator.new(1, :+, 2, :*, 3, :/, 9, :-, 4).calculate
# => -3

# Calculator.new(3, :**, 2, :%, 4).calculate
# => 1