/*
 * Program to compute length of strings various ways, as a silly 
 * example of working with strings.
 *
 * Also shows some other things related to strings.
 */
#include <stdio.h>
#include <string.h>

/* compute length using array and indices */
int string_length_array(char s[]) {
	int i = 0;
	while (s[i] != '\0') { ++i; }
	return i;
}

/* compute length using pointers */
int string_length_ptr(char *s) {
	char *p = s;
	while (*p != '\0') ++p;
	/* p points to \0 */
	return p - s;
}

/* compute length using pointers and recursion */
int string_length_recurs(char *s) {
	if (*s == '\0') {
		return 0;
	} else {
		return 1 + string_length_recurs(s+1);
	}
}

/* try functions above and print input, output */
void test(char *s) {
	printf("string '%s'\n", s);
	printf("length using lib %d\n", (int) strlen(s)); // cast is sloppy
	printf("length using array %d\n", string_length_array(s));
	printf("length using ptr %d\n", string_length_ptr(s));
	printf("length using recurs %d\n", string_length_recurs(s));
	printf("\n");
}

/* main program */
int main(void) {
	test("hello world");
	test("1234");
	test("");

	/* try comparisons */
	char s1[] = "hello";
	char s2[] = "hello";
	printf("s1 == s2? %c\n", (s1 == s2) ? 'y' : 'n');
	printf("s1 equals s2 using strcmp? %c\n", (strcmp(s1, s2) == 0) ? 'y' : 'n');
	return 0;
}