我很抱歉,如果这是一个简单的问题,我是一个初学者。我希望能够从CIN清除输入,如果它不是预期的类型。我有工作的单个字符或价值,但是当我在直线上输入多个字符的问题出现了。
例如,该用户被提示输入一个两倍。如果它不是一个双重我得到一个错误信息,并重新提示。如果我进入一个较长的字符串这也应该发生。
EX 1:预期输出
Enter initial estimate: a
The initial estimate is not a number.
Enter initial estimate: afdf
The initial estimate is not a number.
EX 2:在我的代码目前,非发基金不断阅读,所以我得到:
Enter initial estimate of root : a
The initial estimate was not a number
Enter initial estimate of root : afdf
The initial estimate was not a number
Enter initial estimate of root :
The initial estimate was not a number
Enter initial estimate of root :
The initial estimate was not a number
Enter increment for estimate of root :
The increment was not a number
我一直在使用cin.clear()和cin.get()以及看着函数getline()试图但这并没有工作。
while (numTries < 4)
{
numTries++;
cout << "Enter initial estimate of root : ";
cin >> estimate;
if (!(cin.fail()))
{
if ((estimate >= minEst) && (estimate <= maxEst))
{
break;
}
else
{
if (numTries == 4)
{
cout << "ERROR: Exceeded max number of tries entering data" << endl;
return 0;
}
cout << "" << endl;
cout << "Value you entered was not in range\n";
cout << fixed << setprecision(3) << minEst << " <= initial estimate <= " << maxEst << endl;
}
}
else
{
cout << "\nThe initial estimate was not a number\n";
cin.clear();
cin.get();
}
}
我怎样才能确保输入的下一个时间,它是要输入用于清除?我可以使用函数getline()来实现这一目标?提前致谢。
如果你想坚持使用CIN,那么你将要忽略与cin.ignore()该行的其余部分
#include<limit>
...
double estimate;
do {
if(cin.fail()) {
cin.clear();
cin.ignore(numeric_limits<streamsize>::max(), '\n');
cout << "The initial estimate was not a number" << endl;
}
cout << "Enter initial estimate of root: ";
cin >> estimate;
cout << endl;
} while(!cin);
Getline可能是更好的选择,因为它得到从由换行字符(\ n)的分隔的一个输入流的线。
do {
if(cin.fail()) {
cin.clear();
cout << "The initial estimate was not a number" << endl;
}
cout << "Enter initial estimate of root: ";
} while(!getline(cin, estimate);
你可以retreive输入string和解析它,以检查它是否是一个数字:
bool convert_string_to_double(const std::string &str, double &out_value){
try{
out_value = stod(str);
return true;
} catch (const std::invalid_argument &e) {
return false;
}
}
bool get_double_from_input(double &out_value){
std::string input_str;
cin >> input_str;
return convert_string_to_double(input_str, out_value);
}
然后使用qazxsw POI从输入检索双重价值。如果无法转换值加倍,或返回get_double_from_input
,结果存储到false
它将返回qazxsw POI。