4. 下面是一个结构模板：

struct box
{
  char maker[40];
  float height;
  float width;
  float length;
  float volume;
};

a. 编写一个函数，它将box结构的引用作为形参，并显示每个成员的值。
b. 编写一个函数，它将box结构的引用作为形参，并将volume成员设置为其他3边的乘积。

void show(const box &pst)
{
  std::cout << pst.maker << " " << pst.height << " " << pst.width << " " << pst.length << " " << pst.volume << endl;
}

void product(box &pst)
{
  pst.volume = pst.height*pst.width*pst.length;
}

5. 为让函数fill()和show()使用引用参数。需要对程序清单7.15做哪些修改？

#include <iostream>
#include <array>
#include <string>
const int Seasons = 4;
const std::array<std::string, Seasons> Snames =
{ "春季", "夏季", "秋季", "冬季" };

void fill(std::array<double, Seasons> &pa);  //修改
void show(std::array<double, Seasons> &da);  //修改
int main()
{
  std::array<double, 4> expenses;
  fill(expenses);  //修改
  show(expenses);
  
  system("pause");
  return 0;
}

void fill(std::array<double, Seasons> &pa)  //修改
{
  for (int i = 0; i < Seasons; i++)
  {
    std::cout << "输入 " << Snames[i] << " 支出: ";
    std::cin >> pa[i];   //修改
  }
}

void show(std::array<double, Seasons> &da)  //修改
{
  double total = 0.0;
  std::cout << "\n*****开支*****\n";
  for (int i = 0; i < Seasons; i++)
  {
    std::cout << Snames[i] << ": $" << da[i] << '\n';
    total += da[i];
  }
  std::cout << "总计: $" << total << '\n';
}