isdigit() not working

Code:

---

#include <stdlib.h>
#include <stdio.h>
int main(){
  long x;
  scanf("%ld",&x);
  if(!isdigit(x))
    printf("error");
return 0;
}

---

inputs : a , 1
both inputs prints error
if that problems occurs just because its long how can i check a long type if all it's digits are decimal

isdigit() takes an ASCII character value. This is a little confusing since it is in the form of an "int". Try this:

Code:

---

        printf("%d %d\n", 'a', isdigit('a'));
        printf("%d %d\n", '1', isdigit('1'));

---

And if you are not aware of it:

Ascii Table - ASCII character codes and html, octal, hex and decimal chart conversion
ASCII - Wikipedia, the free encyclopedia

These are the integer->character values used by isdigit() and C char types.

Because it should be

Code:

---

if ( scanf("%ld",&x) == 1 ) {
  // the longest sequence of 0 to 9 was converted to a long int
  // after skipping leading white space.
  // This also includes (and is undiagnosed) excessively long sequences
  // of 0 to 9 which would cause numeric overflow.
} else {
  // first char of input wasn't 0 to 9
}

---

So typing "123abc" extracts 123 as an integer, and leaves "abc" for next time.
Whereas typing "abc123" doesn't do anything at all, and the input stream is still "abc123"

Quote:

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Originally Posted by cable

how can i check a long type if all it's digits are decimal

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Better question: How can a long hold anything but a number?!