Thread: interpretation of a question

Originally Posted by jibbles

i've made the program already. and it all works fine. BUT i think i might have mis interperated the "6 bit code" bit, i just did

Code:

scanf("%d", &code)

and then checked it to be 32||34||2||3

do you guys think i've done that incorrectly? i'm assuming i have. what do you think?

Assuming 'code' is an int, it sounds good to me.

Note that scanf() is probably not the best choice. A smart combination of fgets() and strto[u]l() or sscanf() is probably safer. If you insist, don't forget to test the returned values...

Well a 6-bit code limits the values to be 0..63 inclusive.
So perhaps you need an error message if code is outside this range?

Originally Posted by jibbles

Code:

 
while (code != 32 || code != 34 || code != 2 || code != 3)
{
	printf(options);
	scanf("%d",&code);
}

which doesnt seem to work, i've tried quite a few things, but not getting it.

Your logic is flawed.

Rewrite it in pig-English (forget 'neither-nor'):

"While code is not 32 and code is not 34 and etc."

Got it?

And please check the return of scanf(). What if you type 'a32' by accident? I won't warn you any more about it.

Originally Posted by jibbles

sorry, what do u mean check the return of scanf() i'm unfamiliar with what u are talking about..

I often find myself wondering just what the hell books or instructors are teaching these days...

You don't know how to check the return value of a function?

Code:

int foo( void )
{
    return 1;
}

int main( void )
{
    int bar;

    if( foo( ) == something )
        printf("foo equals something!\n");
    else
        printf("foo does not equal something!\n");

    bar = foo( );
    if( bar == something )
        printf("foo equals something!\n");
    else
        printf("foo does not equal something!\n");

    return 0;
}

You check the return value the same way you check any value. By comparison. There is more than one way to do it. I'll leave it up to you to figure the rest out.

Naturally you'll want to look up the scanf function to see what it actually returns on success and failure.

Quzah.

Originally Posted by jibbles

sorry, what do u mean check the return of scanf() i'm unfamiliar with what u are talking about..

most C-functions return a value. scanf() returns the number of successful conversions. In your case, you are expecting 1. If it returns something else, it means that there was some error. You should warn the user and invite him to try again.

also, i still don't see how my logic is floored?

'floored' ? If you meant flawed, I thougth I have explained it already... Let's try a different approach.

What should be the YES logic :

if (a == 2 || a == 4)

But you want to repeat the process as long as this logic is false. Hence:

while (!(a == 2 || a == 4))

this is correct, and it expands to:

while (a != 2 && a != 4)

according to the boolean logic rules.

http://www.texas.net/~square1/start2a.html

i'm saying while code is not 32 OR is not 34 etc ask for the code again
aren't i?
so when it is 32 or 34, it should exit the while loop..
right?

Wrong! Make the test.

It doesn't return one. It returns the number of stored scans, as shown by this
excerpt from the man page, or else on error:

RETURN VALUES

These functions return the number of input items assigned,
which can be fewer than provided for, or even zero, in the
event of a matching failure. Zero indicates that, while
there was input available, no conversions were assigned;
typically this is due to an invalid input character, such
as an alphabetic character for a `%d' conversion. The
value EOF is returned if an input failure occurs before
any conversion such as an end-of-file occurs. If an error
or end-of-file occurs after conversion has begun, the num-
ber of conversions which were successfully completed is
returned.

[edit]Formatting edit. I still wish it would preserve whitespace...[/edit]

Quzah.

Originally Posted by jibbles

ok i learnt alittle about scanf returning a 1 last semester but i didn't learn to check it (in most cases)
1 = true
0= false

To avoid any misunderstanding, keep in mind that scanf() returns the number of successful conversions.

u reccomend checking that each time u use it?

Yes. If you expect two conversions, the test should be

Code:

   int ret = scanf("%d%d", &a, &b);

   if (ret == 2)
   {
      /* ok */
   }  
   else
   {
      /* error */
   }

etc.

And I also recommend that you write in plain English. Bcz English is nt my fst lng.