Thread: what's the best way to achieve this

Sigh, I think I should give you a working example:

Code:

#include <iostream>
#include <string>
#include <sstream>

int main()
{
    using namespace std;

    int home_score;
    for (;;)
    {
        cout << "Enter the home score: ";
        string line;
        getline(cin, line);
        stringstream ss(line);
        if (ss >> home_score && ss.eof())
        {
            break;
        }
        else
        {
            cout << "Invalid input: enter a number only.\n";
        }
    }

    cout << "You entered: " << home_score << endl;

    return 0;
}

The idea is to read a line as string input from the user. You initialise a stringstream with this line, and then extract from the stream into your desired variable. If the extraction fails, then the input is invalid. Otherwise, you check with the eof() member function: it should return true if there is nothing left to read from the stringstream, otherwise you conclude that the input is invalid due to extra stuff at the end. If the input is valid, you break from the infinite loop, otherwise you print an error message and continue.

Originally Posted by roelof

After the break is there no stack left from the for look ?

What do you mean?

Originally Posted by roelof

I thought that for the for loop there is memory used.
Normal is that the loop ended at the end-argument.
But we use a break now.

Will the memory uses by the for loop be given back or are there pieces of the for loop left behind in the memory ?

You do not have to worry about manual memory management here, and also the variables local to the for loop will be destroyed when control leaves the loop, as is the case for a break.

Originally Posted by roelof

Home_score is a string not a int.

Why is home_score a string?

If you really insist on home_score being a string, then yes, you should use what syzygy suggested. But what you should do is write a function that takes a string and returns true if the string is composed of numeric characters only.

EDIT:
Well, of course, you could rename line to home_score, and home_score to temp, though you would then need to pull out the variable to outside of the loop.

Originally Posted by roelof

I tried but it won't compile

Read the error messages.

• Your for loop syntax is incorrect.
• home_score.at[teller] is wrong. It should be home_score.at(teller) or home_score[teller]
• Comparing with "1" is incorrect. You could compare with '1', but then what about 0s?
• The brace placement of one of your if statements is wrong.
• The condition of one of your if statements lack parentheses.

Other problems:

• a = b is not the same as a == b. This problem occurs in several places.
• You made some effort to indent your code properly, and that is good, but you still can be a little more consistent. Avoid placing consecutive (closing) braces on the same line.
• You can simplify your logic: notice that you do not need to assign true to test in the loop body. In fact, this is why I suggested that you write a function.

As a matter of style, teller is not a conventional name for a variable used as an array/array-like container index. Furthermore, along with test and result, it should be declared in the do while loop, following the rule of thumb to declare variables near first use. In fact, it should be declared in the for loop's initial statement.

Once again, why is home_score a string?