Problem: keep prompting user to enter code until the right they input the right values

Question

I'm having an error with the following code. It's relatively simple but I can't figure out where I'm going wrong. Here's a part of the code:

    int target=0,nextRow;
    char nextCol;

    while(target == 0)
    {
            printf("Enter a valid target: ");
            scanf("%c%d",&nextCol,&nextRow);
            if(nextCol>= 'a' && nextCol <= 'z') /* convert to uppercase */
                    nextCol=nextCol-32;
            if(nextRow>row || nextRow<1 || nextCol<'A' || (nextCol-64)>col)
                    target=0;
            else
                    target=1;
    }

Essentially the user is prompted to input a char and int e.g. B4, C8 etc. Col and Row are predefined integers. If the user-input values are out of bounds target remains as 0. Else target=1 so the loop will exit. When I run this and keep inputing invalid values, "Enter a valid target" starts repeating. Why?

Image of the error

Does this answer your question? [scanf() leaves the new line char in the buffer](https://stackoverflow.com/questions/5240789/scanf-leaves-the-new-line-char-in-the-buffer) — kaylum, May 07 '20 at 12:18
Try: `scanf(" %c%d",&nextCol,&nextRow);` Note extra space before `%c`. See duplicate candidate for explanation. — kaylum, May 07 '20 at 12:19
I don´t think that´s the problem, @kaylum. Read the question twice. — RobertS supports Monica Cellio, May 07 '20 at 12:40
Do you mean "*When I run this and keep inputing **valid** values*" instead of "*When I run this and keep inputing **invalid** values*"? — RobertS supports Monica Cellio, May 07 '20 at 12:41
@kaylum I guess, OP´s intention is to break out of the loop if the user inputs valid values, but it doesn´t seem to work as expected. The second `if` statement seems to be the cause. — RobertS supports Monica Cellio, May 07 '20 at 12:47
@RobertSsupportsMonicaCellio no, I meant when I keep inputting invalid values. This code is supposed to prevent users from inputting the wrong values. I put in invalid values to see if it will let me.. Also, row=4 and col=5 here — Silverleaf7, May 07 '20 at 14:53

RobertS supports Monica Cellio · Answer 1 · 2020-05-07T14:48:37.453

1

Apparently, the condition (nextCol-64)>col seems to be misplaced.

If you input f.e. 'b' as input for nextCol, the expression would be evaluated to 2 > col which seems to be wrong.

Also I consider that col and maybe even row have the value of 0 in which case, the corresponding conditions would always evaluate to true and the loop will never terminate as it seems to do.

Overthink the logic of your program!

edited May 07 '20 at 14:48

answered May 07 '20 at 13:08

RobertS supports Monica Cellio

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Problem: keep prompting user to enter code until the right they input the right values

1 Answers1