Language: C++ (IDE: Visual Studios) How do I make a do while loop return true when a user inputs anything but an integer? I'm a little lost on how to do this.
#include <iostream>//pre processor directive
#include <string>
#include <iomanip>
using namespace std;//standard library
int main( )
double money=0;
do{
cout << ("please enter your taxable income:\n") << fixed << setprecision(2) << endl;
cin >> (money);
}while(money < 0 || );
istream defines a conversion to bool which indicates whether the last read was successful. You can use this to test whether parsing a double succeeded:
if (cin >> money) {
// success
} else {
// failure
}
If the stream is in a failed state and you want to retry reading—e.g., to prompt the user for a new value—then you can use the clear() member function to return the state to normal:
cin.clear();
However, this does not clear the input buffer, so you will end up reading the same data again. You can clear the input buffer until the next newline character:
cin.ignore(numeric_limits<streamsize>::max(), '\n');
Or you can read by lines instead, and use a stringstream to read individual values:
string line;
getline(cin, line);
istringstream stream(line);
if (stream >> money) {
// success
} else {
// failure
}
This has the advantage of forcing user input to be line-based—it’s token-based by default.
I ended up just doing a try/catch statement, which basically involved me adding a new variable to the mix, which is the string "str":
double money = 0; //initialized
string str= ""; //initialized
do{
cout << "Please input an integer value" << endl;
cin >> (str);
try{
money = stod(str); //string to double
}catch(...){ //inside the parenthesis, the "..." means to catch all exceptions.
money = -1;
cin.clear();
}
}while( money < 0);
This will catch anything that does not convert to a double, giving the value of money to equal -1. Otherwise, it will continue with the program.
#include <iostream>//pre processor directive-<3.std::istreamprovides anoperator bool()that lets it be converted to a boolean.