Thread: user input

Hey guys, if I want to get user input for example:

Code:

cout<<"press Y or X"<<endl;
cin>>var

Is there anyway i can use a function like the getch() in this case so if the users enters something other than y or x it will ask them for the input again and not crash the program?

Thanks.

Note that SlyMaelstrom's code doesn't actually check for Y or X for you. You would want to add that check to the while code: while (!(cin >> foo) && foo != 'Y' && foo != 'X')

When reading in a char, only the check against 'Y' and 'X' is necessary, but when you switch your input to read in numbers the extra check of cin >> read will be very helpful.

Thanks for the replies, as its only one character being used is both cin.clear() and cin.ignore both required?

Also how do you loop back so the user can enter their option again once the error message has been displayed? Thanks.

They are not required, but they can help (if the user types in Hello, without the ignore it will display the error once for each letter).

The while loop loops back automatically. After the error message you can add a re-prompt if you want.

I thought it was supposed to do that but when I use it, it doesn't seem to work at all:

Code:

 while (!(cin >> hold) && hold != 'Y' && hold != 'y' && hold != 'X' && hold != 'x')
   cin.clear();
   cin.ignore(); 
cout<<"Please try again"<<endl;

It still doesn't appear to work with the braces.

Sorry, my fault. It should be:

Code:

while (!(cin >> hold) || (hold != 'Y' && hold != 'y' && hold != 'X' && hold != 'x'))
{
   cin.clear();
   cin.ignore(1000, '\n'); 
   cout<<"Please try again"<<endl;
}

You loop while the read fails or the character is not one of the correct inputs.

Also, the ignore() will only ignore a single character, so if the user types a sentence it will not help unless you change it to the way SlyMaelstrom had it (or how I have it above).

Originally Posted by Daved

Sorry, my fault. It should be:

Code:

while (!(cin >> hold) || (hold != 'Y' && hold != 'y' && hold != 'X' && hold != 'x'))
{
   cin.clear();
   cin.ignore(1000, '\n'); 
   cout<<"Please try again"<<endl;
}

You loop while the read fails or the character is not one of the correct inputs.

Also, the ignore() will only ignore a single character, so if the user types a sentence it will not help unless you change it to the way SlyMaelstrom had it (or how I have it above).

Hi, the program seems to go into a loop if the user enters a sentence even with that code I guess its because its a char variable I have to store it in.

>> while (!(cin >> hold)

The operator>> returns the stream which evaluates to true if the stream is in a good state and false if it is in a bad state. So if the read fails, it will evaluate to false. If the read succeeds, it will evaluate to true and the loop won't run any more (unless the other conditions after the or are met). This rarely matters if hold is a char because anything typed by the user is a character and so it shouldn't fail very often. If you were reading into an int or double, and the user typed a charcter like 'a', then the read would fail and that code would trigger the loop to run and display the error message.

>> Hi, the program seems to go into a loop if the user enters a sentence even with that code I guess its because its a char variable I have to store it in.

I don't understand this, maybe you could post your latest code and the example input.

Below is the code I have used and thanks for the explaning the code.

Code:

while (!(cin >> hold) ||(hold != 'Y' && hold != 'y' && hold != 'X'&& hold != 'x'))
		{
			cin.clear();
			cin.ignore(1000,'\n');
			system("cls");
			cout<<"error try again"<<endl;

		}