C++代码出现问题求各位解答

#include <iostream>
using namespace std;
 
class test
{
        const double pi;
    public:
        test(): pi(3.14) { }
        void show()
        {
            cout << "The low-precision pi is " << pi << endl;
            pi = 3.14159;
            cout << "The high-precision pi is " << pi << endl;
        }
};
 
int main()
{
    test A;
    A.show();
}

预期结果：
The low-precision pi is 3.14
The high-precision pi is 3.14159

const double pi;
这是常量，不能修改，去掉 const

 
#include <iostream>
using namespace std;
 
class test
{
        double pi;
    public:
        test(): pi(3.14) { }
        void show()
        {
            cout << "The low-precision pi is " << pi << endl;
            pi = 3.14159;
            cout << "The high-precision pi is " << pi << endl;
        }
};
 
int main()
{
    test A;
    A.show();
}

• 这有个类似的问题, 你可以参考下: https://ask.csdn.net/questions/7553099
• 这篇博客也不错, 你可以看下C++代码实现获取系统时间精确到毫秒级
• 除此之外, 这篇博客: C++ 形参初始化及析构顺序中的 测试代码： 部分也许能够解决你的问题, 你可以仔细阅读以下内容或跳转源博客中阅读:
  

• #include <iostream>
  using namespace std;
  class Test
  {
  public:
  	Test(int);
  	Test(Test&);
  	~Test();
  
  private:
  	int a;
  };
  
  Test::Test(int i)
  {
  	a = i;
  	cout << "constructing  " << a << endl;
  }
  Test::Test(Test& test)
  {
  	a = test.a;
  	cout << "copying   " << a << endl;
  }
  
  Test::~Test()
  {
  	cout << "destructing   " << a << endl;
  }
  
  void outPut(Test test1, Test test2);
  
  int main() {
  	Test* a = new Test(3);
  	Test test1(1);
  	Test test2(2);
  	outPut(test1, test2);
  	system("pause");
  	return 0;
  }
  void outPut(Test test1, Test test2) {
  }
  

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