/*
 * determine whether a string is a palindrome 
 */
#include <stdio.h>
#include <stdbool.h>
#include <string.h>
#include <ctype.h>

bool is_palindrome(char *s) {
    char *p = s; /* start at first char and go forward */
    char *q = s + strlen(s) - 1; /* start at last char and go back */
    while (p < q) {
        while (!isalpha(*p)) ++p;
        while (!isalpha(*q)) --q;
        if (p >= q) return true;
        if (tolower(*p) != tolower(*q)) return false;
        ++p; --q;
    }
    return true;
}

void test_palindrome(char *s) {
    printf("'%s' %s a palindrome\n", s, is_palindrome(s) ? "is" : "is not");
}

int main(void) {
    char line[80];
    printf("enter a line of text, or \"tests\" for tests/examples\n");
    fgets(line, sizeof line, stdin);
    char *eol = strchr(line, '\n');
    if (eol == NULL) {
        printf("line too long, maximum %d\n", (int) sizeof line - 1);
        return 1;
    }
    *eol = '\0';
    if (strcmp(line, "tests") == 0) {
        test_palindrome("a");
        test_palindrome("ab ba");
        test_palindrome("abcd");
        test_palindrome("abba");
        test_palindrome("A man, a plan, a canal -- Panama!");
    } else {
        test_palindrome(line);
    }
    return 0;
}