isalpha

why does this function crash my program :(

Code:

---

int checkPrice (int *num)
{
        scanf ("%d", num);
        while (isalpha (*num))
        {
                fflush (stdin);
                printf("Only numerals allowed\n");
                printf("Please re-input the price: ");
                scanf ("%d", num);
                return 0;
        }               
        fflush (stdin);
        return 1;
}

---

num is being passed by reference..
basically, it works if i input a number but if i input a character it crashes :( and thats the exact thing i want to test in the program..
any other ways around it
:)

It works fine to me! can we see the full code?!
why did u include return 0 in the while loop?!

my friend tested a number with isalpha and it worked and i did almost same thing and it didnt... point being that isalpha can test integers :)

Quote:

---

Originally posted by Salem
isalpha tests characters, not numbers

Code:

---

while ( scanf("%d", num ) != 1 ) {
    while ( getchar() != '\n' );  // better than fflush(stdin)
    printf("Only numerals allowed\n");
    printf("Please re-input the price: ");
}

---

---

i dont quite get ur first line of code...

what happens if a user inputs 22442a

will that line of code work for that

Salem, in your first line of code:

Quote:

---

Code:

---

while ( scanf("%d", num ) != 1 ) {
    while ( getchar() != '\n' );  // better than fflush(stdin)
    printf("Only numerals allowed\n");
    printf("Please re-input the price: ");
}

---

---

should it not read:

Code:

---

while (scanf ("%d", &num) !=1 ) {
/* rest of code here */

---

I always thought the & was necessary when using scanf?!?!:confused:

num is a pointer which contain an address therefore there is no need for &!

Thankyou for clearing that up Lazystudent!:D

whoa
salem dude, u r a genius :)
but u know what even though it works, i still dont get why should it keep reading till != 1 ??? :)

i read the C reference manual but it didnt make sense till u gave ur explanation
thanks mate :)

Of course, it's quite possible that the whole reason your code was crashing was this line:

fflush (stdin);

After all, it's undefined. Theoreticly, it could crash your program.

Quzah.