我正在阅读以下格式的文件
1001 16000 300 12.50
2002 24000 360 10.50
3003 30000 300 9.50
其中项目是：贷款ID、本金、月份、利率。
我不确定我的输入字符串流做错了什么，但我没有正确读取这些值，因为只有贷款 ID 被正确读取。其他一切都是零。对不起，这是一个家庭作业，但我只是想知道你是否能帮助我找出我的错误。
if( inputstream.is_open() ){
/** print the results **/
cout << fixed << showpoint << setprecision(2);
cout << "ID " << "\tPrincipal" << "\tDuration" << "\tInterest" << "\tPayment" <<"\tTotal Payment" << endl;
cout << "---------------------------------------------------------------------------------------------" << endl;
/** assign line read while we haven't reached end of file **/
string line;
istringstream instream;
while( inputstream >> line ){
instream.clear();
instream.str(line);
/** assing values **/
instream >> loanid >> principal >> duration >> interest;
/** compute monthly payment **/
double ratem = interest / 1200.0;
double expm = (1.0 + ratem);
payment = (ratem * pow(expm, duration) * principal) / (pow(expm, duration) - 1.0);
/** computer total payment **/
totalPayment = payment * duration;
/** print out calculations **/
cout << loanid << "\t$" << principal <<"\t" << duration << "mo" << "\t" << interest << "\t$" << payment << "\t$" << totalPayment << endl;
}
}