/* File: pali2.c
   Checks if a string is a palindrome.
*/

#include<stdio.h>
#include"genlib.h"
#include"simpio.h"
#include"strlib.h"

/* Function Prototype */
bool IsPalindrome(string str) ;


main() {
   string str ;

   printf("This program checks for palindromes.\n") ;
   printf("End the program by entering a blank line.\n") ;
   while (TRUE) {
      printf("String: ") ;
      str = GetLine() ;
      if ( StringEqual(str, "") ) break ;
      if ( IsPalindrome(str) ) {
	 printf("'%s' is a palindrome.\n", str) ;
      } else {
	 printf("'%s' is not a palindrome.\n", str) ;
      }
   } /* end while */
}

/* Function: IsPalindrome */
bool IsPalindrome(string str) {
   char front, back ;
   int head, tail ;

   head = 0 ;
   tail = StringLength(str) - 1 ;
   while (head < tail) {
      front = IthChar(str, head) ;
      back = IthChar(str, tail) ;
      if (front != back) return(FALSE) ;
      head++ ;
      tail-- ;
   }
   return(TRUE) ;
}