Thread: 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"

Originally Posted by cable

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

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