Thread: Numeral verification

Hi everyone!

We were assigned a project not too long ago that asks us to ask a user to input numbers into a matrix. The user also chooses its dimensions.

My questions is how would I incorporate a validation for the dimensions. Obviously, the only valid dimensions are numerical so I want an error to display if the user types a letter or a special character such as apostrophe or backslash.

My thoughts:

I was thinking that I could have it check the ASCII numerical value and limit those that range from 48 - 57 (numbers 0 - 9) but I cannot seem to get this to work. I would want the number that the ASCII code refers to be used as the dimensions not (48 - 57). Maybe there is an easier way to do this?

Code:

int main(void)
{
//Declare necessary variables
int rowSize = 0;
int columnSize = 0;

do
{     //Beginning of column while loop

printf("Please enter the number of columns: ");
scanf("%d", &columnSize);

//Verify column size
if (columnSize > 10)
printf("ERROR: The maximum number of columns is 10.\n");
else if(columnSize < 0)
printf("ERROR: Invalid number of columns.  Must be greater than 0.\n");
}
while (columnSize > 10 || columnSize < 0);

... Same for the row of the matrix.

Thanks for any and all help!

You need to check the return value of scanf().... You can look it up in your C Library documentation.

Hi Tater,

I'm not sure how to check the return value because I'm using Putty, a remote logon unix program. Any suggestions? Maybe you or someone else knows how to do that. I'm somewhat new to programming. I have a basic understanding but I would not call myself proficient or knowledgeable about C.

Originally Posted by ButtahNBred

I'm not sure how to check the return value because I'm using Putty, a remote logon unix program. Any suggestions?

You do it the same way you wrote the rest of the code; With a text editor

scanf(), fscanf()

Code:

int returnvalue = scanf(...);

Originally Posted by ButtahNBred

I'm not sure how to check the return value because I'm using Putty,

That ... is one of the best non sequiturs ever. You use the return value of scanf just like you would use the return value of any other function, like sqrt:

Code:

foo = sqrt(9);
foo = scanf(...);

Alternatively, you can use getchar + isdigit.

hahaha. Well, I'm dumb. I know what a return value is.

Thanks for the help. Hopefully, I will be able to make some more progress...