Thread: Help with some quick questions.

Originally Posted by jp5a9852

My second question is: is it legal to use a while statement like this?
while(op == + || - || * || /)

No it is not.

There are plenty of other problems in your "code" as well. But the nature of them makes it obvious you are just tapping away at your keyboard, rather than trying to understand how C works. It would be a waste of time for anyone else attempting to correct it, since you are not actually trying to understand, and will not understand the changes they might make.

Try actually reading any half decent textbook or tutorial before proceeding further.

You're kidding, eh, camel-man.

Originally Posted by camel-man

Well not really? lol I mean is not that the correct syntax? Now whether or not that is logically the right way about doing this is extremely questionable

Just to be clear, I wrote my "you're kidding" comment BEFORE you inserted single quote characters into the code sample.

By "reverse" a number, do you mean reverse the digits in the number?
ie., 91 becomes 19?


There is an easy way to reverse numbers, if you take the number in, as digits in a string, but if it's an int, for instance, it can be done by "peeling" the digits off the 1's column, one at a time, like so:

Code:

#include <stdio.h>

int main(void) {
   int i,one,n=1234567;
   char digits[8] = {""};
   i=sizeof(digits)-1;
   digits[i]='\0';
   i=0;
   while(n>0) {
      one=n%10;
      digits[i++]=one+'0';
      n/=10;  
   }
   printf("%s\n",digits);
   return 0;
}

If you need the digits to be an actual number, use sscaf(digits, "%d", &n); and then print out n.

For a while loop, you have to have it "set up" before the while() is reached by the program. That's where the test is made by the program, and only if the test return true (non-zero), will the rest of the loop be executed.

That while loop test makes me reach for the Pepto Bismol.

If your teacher is requiring you to reverse digits in floating point, s/he should be summarily fired for incompetence. If you have decided you need to use floating point variables, you are badly mistaken.

Floating point representations are an approximation, so many attempts to reverse digits will also be an approximation (i.e. inaccurate). Work with integral values instead.

For example, a floating point variable cannot represent 0.1 exactly. So, using floating point operations, there is no way to even reverse 1.234 to obtain 432.1 (since a floating point variable can't exactly represent 432.1). The only way you can do it is read two integers separated by a '.', reverse the digits on those, and output the two integers in reverse order (second before first). And, even if you do that, it is not possible to store the result in a floating point variable. So work with integers instead.

My teacher never specified whether it was supposed to be float or int, so I'll use int, thanks.

I've revised my code, this is what I have now. I can see why you were mad at my code earlier, it was nonsensical The reverse = 3; was just to test if it would work this far.

Code:

#include <stdio.h>
#include <ctype.h>


int main(void)
{
    int num, sum, reverse;
    char op, ans;


    printf("This program solves a five digit or smaller number and it reversed.\n");


    do
    {
    printf("Enter the operator you wish to use (+, -, /, *): ");
    scanf(" %c", &op);


    printf("Enter a 5 or less digit number: \n");
    scanf(" %d", &num);


    
    reverse = 3;


    if (op == '+')
        sum = num + reverse;
    if (op == '-')
        sum = num - reverse;
    if (op == '*')
        sum = num * reverse;
    if (op == '/')
        sum = num / reverse;
    
    printf(" %d", sum);
    
    printf("\nWould you like to continue? Y or N?: ");
    scanf(" %c", &ans);


    }
    while (toupper(ans) == 'Y');


    
    printf("Press any key to exit.\n");


getchar();
getchar();
return 0;


}

Originally Posted by jp5a9852

I can see why you were mad at my code earlier, it was nonsensical

I wasn't mad. But, yes, the "code" in your first post was completely nonsensical and, if anything, my initial comments were gentler than warranted.