/* Using character test macros to create an integer */
/* input function. */

#include <stdio.h>
#include <ctype.h>

int get_int(void);

main()
{
     int x;
     x =  get_int();
     printf("You entered %d.", x);
     return(0);
}

int get_int(void)
{
     int ch, i, sign = 1;

     /* Skip over any leading white space. */

     while ( isspace(ch = getchar()) )
         ;

     /* If the first character is non-numeric, unget */
     /* the character and return 0. */

     if (ch != '-' && ch != '+' && !isdigit(ch) && ch != EOF)
     {
         ungetc(ch, stdin);
         return 0;
     }

     /* If the first character is a minus sign, set */
     /* sign accordingly. */

     if (ch == '-')
         sign = -1;

     /* If the first character was a plus or minus sign, */
     /* get the next character. */

     if (ch == '+' || ch == '-')
         ch = getchar();

     /* Read characters until a non-digit is input. Assign */
     /* values, multiplied by proper power of 10, to i. */

     for (i = 0; isdigit(ch); ch = getchar() )
         i = 10 * i + (ch - '0');

     /* Make result negative if sign is negative. */

     i *= sign;

     /* If EOF was not encountered, a nondigit character */
     /* must have been read in, so unget it. */

     if (ch != EOF)
         ungetc(ch, stdin);

     /* Return the input value. */

     return i;
}