意外舍入双变量 C++

Question

题主总是四舍五入0.x而且答案是错误的

我正在使用 code:blocks mingw

请查看交易 2 上的这张图片，它是 99855.7-145.022，但答案已经四舍五入

#include <iostream>
using namespace std;

int main()
{
    double x,amort,principalminus,interest,amortbal,theo,adv,advtemp,paid,mri;
    double principal;
    char con;
    adv=0;
    cout<<"CMP Calculator "<<endl;
    cout<<"Base Principal:";
    cin>>principal;
    cout<<"MRI:";
    cin>>mri;
    cout<<"Monthly Amortization:";
    cin>>amort;
    do
    {
      x++;
      interest = (principal*0.06)/12;
      cout<<"Number of transaction:"<<x<<endl;
      cout<<"Amortization amount paid:";
      cin>>paid;
      if(paid>=685.3)
      {
        principalminus = amort - (interest+mri);
        advtemp = paid-amort;
      }
      principal=principal-principalminus;
      adv=adv+advtemp;
      cout<<"Interest:"<<interest<<endl;
      cout<<"Principal Paid:"<<principalminus<<endl;
      cout<<"Advance:"<<adv<<endl;
      cout<<"Total Principal:"<<principal<<endl;

      cout<<"Do you want to continue?:[Y/N]";
      cin>>con;
      cout<<endl<<endl;
    }
    while(con=='Y'||con=='y');

    return 0;
}

Answer 1

it's 99855.7-145.022 but the answer is already rounded up

你只需要打印更多的数字，例如：

cout << std::setprecision(15);

在其他打印之前的某个地方，为此你需要

#include <iomanip>

你将拥有

pi@raspberrypi:/tmp $ ./a.out
CMP Calculator 
Base Principal:100000
MRI:41
Monthly Amortization:685.3
Number of transaction:1
Amortization amount paid:686
Interest:500
Principal Paid:144.3
Advance:0.700000000000045
Total Principal:99855.7
Do you want to continue?:[Y/N]y


Number of transaction:2
Amortization amount paid:686
Interest:499.2785
Principal Paid:145.0215
Advance:1.40000000000009
Total Principal:99710.6785
Do you want to continue?:[Y/N]n

Total Principal 的打印值是正确的，无论如何根据定义理解任何浮点数的精度都有限制，您可以在打印值中看到前进.

如果您的编译器支持 long double，您可以使用它们，同时要求打印 20 位数字，结果将是：

bruno@bruno-XPS-8300:/tmp$ ./a.out

CMP Calculator 
Base Principal:100000
MRI:41
Monthly Amortization:685.3
Number of transaction:1
Amortization amount paid:686
Interest:499.99999999999998149
Principal Paid:144.30000000000001853
Advance:0.7000000000000000111
Total Principal:99855.699999999999982
Do you want to continue?:[Y/N]y


Number of transaction:2
Amortization amount paid:686
Interest:499.27849999999998143
Principal Paid:145.02150000000001856
Advance:1.4000000000000000222
Total Principal:99710.678499999999964
Do you want to continue?:[Y/N]n

还请注意，您错过了用 0 初始化 x，它可以是 int 而不是 double

意外舍入双变量 C++

unintended round up double variable c++

c++

codeblocks