计算输出= nan？

Question

首先,这是一个课堂作业,所以我会很感激帮助,但只是提示,因为我想学习.我必须根据我的代码中的利率等计算每月付款,但我的计算结果不合适.我的输出读取nan我相信的not a number.我一直试图弄清楚我哪里出错无济于事,有关如何纠正这个问题的任何建议？提前致谢.

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

int main()
{
    //collect payment info
    double loanAmount = 0; 
    double anualRate = 0;
    double monthlyIntRate = 0; 
    int numOfPayment = 0; 
    double monthlyPayment = 0; 
    double amountPaidBack = 0; 
    double interestPaid = 0;

    cout << "Enter loan amount: ";
    cin >> loanAmount;
    cout << "Enter Anual Interest Rate: ";
    cin >> anualRate;
    cout << "Enter Payments made: ";
    cin >> numOfPayment;

    //calculate montly payment
    monthlyPayment = (loanAmount * pow(monthlyIntRate + 1, numOfPayment) * monthlyIntRate) / ( pow(monthlyIntRate + 1, numOfPayment) - 1);                                                    

    //calculate amount paid back
    amountPaidBack = monthlyPayment * numOfPayment;

    //calculate interest paid
    monthlyIntRate = anualRate / 12;
    interestPaid = monthlyIntRate * numOfPayment;

    //split input from calculated output
    cout << "-----------------------------\n" << endl;

    //Display the calulated data
    cout << fixed;
    cout << setprecision(2);

    cout << "Loan Amount: " << setw(15) << "$ "<< right << loanAmount << endl;

    cout << "Monthly Interest Rate: " << setw(14) << monthlyIntRate << "%" << endl;

    cout << "Number of Payments: " << setw(17) << numOfPayment << endl;

    cout << "Montly Payment: " << setw(19) << "$ " << monthlyPayment << endl;

    cout << "Amount Paid Back: " << setw(17) << "$ " << amountPaidBack << endl;

    cout << "Interest Paid: " << setw(18) << "$ " << interestPaid << endl;

    return 0;

输出:

Loan Amount:              $ 100000.00
Monthly Interest Rate:           1.00%
Number of Payments:                36
Montly Payment:                  $ nan
Amount Paid Back:                $ nan
Interest Paid:                 $ 36.00

Answer 1

你除以零.它发生在这一行:

monthlyPayment = (loanAmount * pow(monthlyIntRate + 1, numOfPayment) * monthlyIntRate) / ( pow(monthlyIntRate + 1, numOfPayment) - 1);

存储的值monthlyIntRate为零,因此pow(monthlyIntRate + 1, numOfPayment)eqauls为(0 + 1) ^ numOfPayment,因此pow(monthlyIntRate + 1, numOfPayment) - 1)为0.

Answer 2

正如@FlopCoder所提到的,按时间monthlyPayment计算,monthlyIntRate == 0.所以分数的除数

monthlyPayment = (loanAmount * pow(monthlyIntRate + 1, numOfPayment) * monthlyIntRate) / ( pow(monthlyIntRate + 1, numOfPayment) - 1);

是0.

但这还不够nan.如果股息不是0,你会得到inf.但是你的情况也是 0.然后,你明白了nan.