/* expands shorthand notation like a-z in s1 into the equivalent
 * complete list abc...xyz in s2
 */

#include <ctype.h>

void expand(char s1[], char s2[]) {
     int i, j, k, step;
     
     for (i = j = 0; s1[i] != '\0'; i++) {
	  if (isalnum(s1[i])) {
	       if (s1[i+1] != '-' || !isalnum(s1[i+2]))
		    continue;
	       step = (s1[i] > s1[i+2]) ? -1 : 1;
	       for (k = 0; (s2[j++] = s1[i]+k) != s1[i+2]; k += step);
	       s2[j] = '\0';
	       i++;
	  } else if (s1[i] == '-' && i == 0) {
	       s2[j++] = '-';
	  }
     }

     if (s1[i-1] == '-') {
	  s2[j++] = '-';
	  s2[j] = '\0';
     }
}

int main(void) {
     char s[30], t[1000];

     printf("foo: ");
     scanf("%s", s);
     putchar('\n');
     expand(s, t);
     printf("%s\n", t);

     return 0;
}