c++ - c++ 中的 csv 文件管理（具体设置标题和每个标题将分别具有的值）

Question

所以我会发布我的代码，然后在下面问我的疑问，这不是作业，我正在练习我表弟的旧作业，所以请冷静一下，因为这是作业，所以不帮助你。

#include <iostream>
#include <fstream>
#include <cmath>
using namespace std;

class Loan{
 public:
  Loan();
  float principle;
  float months;
  float interest;
  float monthly_payments();
  float accrued();
  float remaining_bal();
};

float Loan::monthly_payments() {
  float payment;
  float j = interest/12;
  payment = j * principle /(1 - pow((1 + j), -1 * months));
  return payment;
}
Loan::Loan() {

}
float Loan::accrued() {
  float j = interest/12;
  float accrued = j*principle;
  return accrued ;
}
float Loan::remaining_bal() {
  float x = monthly_payments();
  float y = accrued();
  float remaining = principle - x + y;
  return remaining;
}

int main() {
  char filename[16]; //this will allow the file name be 16 in length
  cout << "Enter the name of an existing file: ";
  cin.getline (filename,16);

  cout << "\nThe name of your file is: " << filename << endl;

  ofstream myFile; // this will allow for file to be saved
  myFile.open (filename); // open file named: myFile

  if( myFile.good() )
    cout << "\nFile open is OK \n";
  else
    cout << "\nfile open FAILED \n";

  Loan l1;
  cout<<"Enter principle, months and interest rate"<<endl;
  cin>>l1.principle>>l1.months>>l1.interest;
  float x = l1.principle;
  float y = l1.months;
  float z = l1.interest;
  float accrued = l1.accrued();
  float monthly = l1.monthly_payments();
  float remaining = l1.remaining_bal();

  while (remaining > 0){
    myFile<<"month"<<"beginning balance"<<"monthly interest"<<"accrued interest"<<"final balance";

  }
  return 0;
}

这就是我到目前为止所拥有的，现在我想要上面的列，并以 csv 文件的形式分别将值添加到每个列中，棘手的部分是这些值在每次迭代时都会更新，所以我坚持如何从这里开始。任何帮助将不胜感激。

谢谢！

标签： c++csv

Answer 1

你在公式中犯了一些错误。

要获取下个月的值，您需要计算新月份的值（基于当前值），然后继续计算。

不幸的是，在我看来，您的结构或一般方法中也存在设计问题。但我尽可能地保留了你的原始设计。请尝试重构。

我更正了公式。

而且，我添加了循环的值。这些现在包括一些计算，以获得本月的当前值。然后我们把剩余的余额作为当前余额。然后我们继续运行循环。

为了统计目的，我还做了一些积累。

请尝试一下，并输入扩展名为“.csv”的文件名。然后您可以使用 Excel 打开文件后记。你会看到你的桌子。当然你也可以用notepad++打开。

我还更新了一些编程风格问题。

请参见

#include <iostream>
#include <string>
#include <fstream>
#include <cmath>
#include <iomanip>

class Loan {
public:
    Loan() {}
    long double principal;
    long double months;
    long double interest;
    long double monthlyPayment();
    long double accrued(long double currentBalance);
    long double remainingBalance(long double currentBalance);
};

inline long double Loan::monthlyPayment() {
    const long double interestPerMonth = interest / 100.0 / 12.0;
    const long double temp = std::pow((1.0 + interestPerMonth), months);
    return principal / ((temp - 1) / (interestPerMonth * temp));
}

long double Loan::accrued(long double currentBalance) {
    long double j = interest / 12 / 100;
    long double accrued = j * currentBalance;
    return accrued;
}
long double Loan::remainingBalance(long double currentBalance) {
    long double x = monthlyPayment();
    long double y = accrued(currentBalance);
    long double remaining = currentBalance - x + y;
    return remaining;
}

int main() {

    // Get filename
    std::cout << "Enter the name of an existing file: ";
    if (std::string fileName; std::cin >> fileName) {
        // Show fielname again
        std::cout << "\nThe name of your file is: " << fileName << "\n";
        // Try to pen file and check, if it could be opened
        if (std::ofstream myFile(fileName); myFile) {
            // Give positive feedback
            std::cout << "\nFile open is OK\n\n";

            // Define structure
            Loan l1;

            // Get data from user
            std::cout << "Enter principal, months and interest rate" << std::endl;
            std::cin >> l1.principal >> l1.months >> l1.interest;

            // Calculate the monthly rate
            long double monthly = l1.monthlyPayment();

            // Show some statistics
            std::cout << "\n\nMonthly payment will be:  " << monthly << "\n\n Resulting table:\n\n";

            // We want to sum up some values for further statistics
            long double overallInterest = 0.0;
            long double overallRate = 0.0;
            long double overallPaidBack = 0.0;

            // Display header
            myFile << std::right << std::setw(11) << "Month;" << std::setw(16) << "Balance;" << std::setw(11) << "Rate;" <<
                std::setw(11) << "Interest;" << std::setw(11) << "Paid;" << std::setw(16) << "Final\n";

            // Get initial values for calculations
            long double currentBalance = l1.principal;
            unsigned int month = 1;

            // float has always rounding errors. We ignore everything below 0.1
            while (currentBalance > 0.1) {

                // The interes rate for this month
                long double accrued = l1.accrued(currentBalance);
                // Overall, for statistics
                overallInterest += accrued;

                // What is the balance after this month
                long double remainingBalance = l1.remainingBalance(currentBalance);

                // Output values in CSV format
                myFile << std::right << std::setw(10) << month << ";" << std::setw(15) << currentBalance <<
                    ";" << std::setw(10) << monthly << ";" << std::setw(10) << accrued << ";" << std::setw(10) << monthly - accrued
                    << ";" << std::setw(15) << remainingBalance << "\n";

                // Set start point for next month
                currentBalance = remainingBalance;
                // Now we will look at next months
                ++month;
                // Calculate statistical values
                overallRate += monthly;
                overallPaidBack += (monthly - accrued);
            }

            // Show some statistics on sceen
            std::cout << "\nOverall paid interest: " << overallInterest << "\nOverall paid rates:    " << overallRate
                << "\nOverall paid:          " << overallInterest + overallRate
                << "\n\nFor loan of:           " << overallPaidBack << "\n";
        }
        else {
            std::cerr << "**** Error. File '" << fileName << "' could not be opened.\n";
        }
    }
    return 0;
}