Re: [Dev-C++] integer to string

[Luigi S. <gi...@li...>]

On Tue, Apr 01, 2003 at 02:42:48AM +0000, Khalid El-Kary wrote:
> Hi fellows,
> 
> I'm wondering if there's a possible way to turn an integer to its string 
> representation in C
> 
> //I want to get a string "5" out of f
> int f=5;
> 
> thanx in advance.
> 
> Regards,
> Khalid Al-Kary
> 

Hello Khalid,

You have already been supplied with an excellent solution, here is
another approach, both: less efficient and less elegant; but I'm posting 
it anyway because I feel it is an example some newbies (like me) can 
probably benefit from.

t_itoa.c
--------
#include <stdio.h>
#include <stdlib.h>
#include "itoa.h"

/********************************************************************/
int
main()
{
  int k = 123;       /* integer value to be converted */
  char *s = itoa(k); /* string holding the converted value */

  printf("INPUT:\nk = %d\n\n", k);
  printf("OUTPUT:\ns = %s\n\n", s);
  free(s); /* return memory to the system, as soon as you can */

  k = -4567; /* a little harder: using a negative number */
  s = itoa(k);
  printf("INPUT:\nk = %d\n\n", k);
  printf("OUTPUT:\ns = %s\n\n", s);
  free(s);
  
  return 0;
}
--------





itoa.h
------
#ifndef itoa_h
#define itoa_h
#pragma defs_in itoa.c  /* needed by makefile generator (ignore it) */
/********************************************************************/

/* turn an integer into a string (i.e. an array) */
char *
itoa(int n);

/* invert order of elements in an array */
char *
invert(char *s);

/********************************************************************/
#endif /* not itoa_h */
------




itoa.c
------
#include <stdlib.h>
#include <assert.h>
#include <string.h>
#include "itoa.h"

#define MAXSZ   21  /* assuming integer is made of 19 digits + sign */ 
/********************************************************************/
char *
itoa(int n)
{
  char * buf = (char *)calloc(MAXSZ, sizeof(char)); /* get memory */
  char *p = buf; /* pointer used to sweep across buffer */
  char neg = 0;  /* 1 means that the integer is negative */

  assert(buf != 0); /* check if memory was allocated */

  if (n < 0) /* negative integer */
    {
      n = -n;  /* work on its absolute value */
      neg = 1; /* turn on the flag */
    }

  while (n)  /* main loop */
    {
      *p++ = '0' + n % 10; /* char for a digit as offset from '0' */
      n /= 10; /* drop last character */
    }

  if (neg) /* append a negative sign */
    *p++ = '-';
  
  *p = '\0'; /* terminate string */
  return invert(buf);
}

/********************************************************************/
char *
invert(char *s)
{
  char *p = s + strlen(s); /* points the terminating '\0' */
  char *q = s - 1;         /* points one before first char */

  while (--p > ++q)
    {
      char c = *p; /* classic code used to swap characters */
      *p = *q;
      *q = c;
    }

  return s;
}
------


Regards
-- 
>> gisan >>