Thread: integer problems

hi, I would like my program to nottice something, like a letter, and give an error, right now its just transforming it to an int, a very large one, and using the wrong error msg...here is my code

#include <stdio.h>




unsigned int getInputData(){
unsigned int digit;
printf("Please Enter in a positive number, then hit ENTER\n");
scanf("%d", &digit);

printf("The number you entered is: %d\n", digit);

if (sizeof(digit) > 2)
printf("Fatal error: Integer size too large\n");
else if (digit==0)
printf("That is not an Integer");
else
printf("Good, you've entered an integer!");
return(digit);
}

int main(void){

getInputData();
return(0);
}

so like say when i run it, I type in 'hello' instead of an int, first it tells me i entered soemthing like
The number you entered is: -1073743180

then it gives me the integer too large error, but I want it to give me the other error...please help me!

well, see I can't use strings or arrays i can only use the usual I/O method functions to read single characters only

Oh, that's what you wanted to do :-)

Code:

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <limits.h>

unsigned int getInputData(){
  char *p;
  char *end;
  char buff[25];
  unsigned long digit;

  printf("Please Enter in a positive number, then hit ENTER\n");
  if (fgets(buff, sizeof(buff), stdin) == 0)
  {
    printf("Fatal error: No input\n");
    return 0;
  }

  if ((p = strrchr(buff, '\n')) != 0)
    /* Remove the newline */
  {
    *p = '\0';
  }

  errno = 0;
  digit = strtoul(buff, &end, 0);
  
  if (errno == ERANGE)
    printf("Fatal error: Out of range\n");
  else if (end == buff || end < buff+strlen(buff))
    printf("Not an integer\n");
  else
    printf("Good, you've entered an integer!\n");

  return(digit);
}

int main(void){
  getInputData();

  return(0);
}

so like say when i run it, I type in 'hello' instead of an int, first it tells me i entered soemthing like
The number you entered is: -1073743180

then it gives me the integer too large error, but I want it to give me the other error...please help me!

You should test the input for an invalid data type error before testing anything since the program has gone loopy

Code:

#include <stdio.h>
#include <limits.h>

int main( void )
{
  int num1;
	
  printf("Enter a string or a number: ");
	
  if(scanf("%i", &num1) != 1)
  {
    printf("I know that I said enter a string...");
    return -1; /* input stream error */
  }	
	
  else if(num1 > SHRT_MAX)
  {
    printf("Whoa that's a big number... oops");
    return -1;
  }
	
  printf("Good you didn't fall for it as you entered %i\n"
             , num1);
  
  return 0;
}

[edit]Doh Cela...... explained it better

I can't really use anything i haven't learned yet, so i can't implement limits.h, and use the SZE_Max or whatever it was...I was told to use the SizeOf function, basically, the getInputData function gets characters one at a time and if the character is a digit then the result should be stored in an "int". if there are illegal characters or if the integer is too large, then the remaining characters are discarded until a carriage return is found...and the user should then be prompted again...

You can't use sizeof to determine to contents of a variable, as its for telling you the size of the variable itself.

To do what you ask, you'll need to check the return code from scanf(). If it isn't 1, then use this loop to empty the input buffer, then prompt and read another int.
>while (getchar() != '\n');

#include <stdio.h>




unsigned int getInputData(){
unsigned int digit;
printf("Please Enter in a positive number, then hit ENTER\n");



if (scanf("%d", &digit) !=1){
printf("That is not an integer\n");
return(-1);}
else if (sizeOf(digit)>4){
printf("That integer is way too large!");
return(-1);}
else
printf("Good, you've entered an integer!");
printf("The number you entered is: %d\n", digit);
return(digit);
}

int main(void){

getInputData();
return(0);
}