Thread: error checking

Hi, I am a high school student taking C++.

I had to write a program which takes in a number and lists all of the primes less than or equal to that number.

That I did no problem.

Now the teacher would like us to check the input to be sure that it is allowable.

I have read the FAQ and still don't understand how to take in a string (C++ style) and convert it to an int. Could someone help.

Or is that the best way to do it??

string user_input;
cout << "Please enter a positive integer: ( 0 to quit )";
cin >> user_input;

So I need to be sure that the user has entered a positive integer or 0. If 0 then quit. If not a positive int then I need to ask again.

We have not covered pointers yet so I don't know how to use them. Any help or a link to a place that could help would be much appreciated.

Hi I appreciate the response!

When I tried to compile, I got the following error:

cannot convert `user_input' from type `string' to type `const char *'

with the line number with the atoi function on it.

This is the same problems I was having when trying to implement it.

I thought that you can not use atoi on a C++ string, and that it only works on C style strings. But I am having trouble with that as well.

Thanks