#ifdef TEST_LLIST
#include <stdio.h>
#endif /* TEST_LLIST */

#include <stdlib.h>

typedef struct node {
	void* data;
	struct node* next;
} node_t;

node_t* new_node(void* data) {
	node_t* node = malloc(sizeof(node_t));
	node->data = data;
	node->next = NULL;
	return node;
}

void* list_head(node_t* n) {
	return n->data;
}

node_t* list_tail(node_t* n) {
	return n->next;
}

/* appends node to end of ls, returns ls
   (obviously) linear in size of ls */

node_t* list_append(node_t* ls, node_t* node) {
	node_t* current = ls;
	
	if (ls == NULL) return node;
	
	while(current->next) current = current->next;
	
	current->next = node;
	
	return ls;
}

/* prepends node to beginning of ls, returns new ls
   (obviously) constant-time */

node_t* list_prepend(node_t* ls, node_t* node) {
	node->next = ls;
	return node;
}

/* frees all storage associated with a list (but NOT all data!) */
void list_cleanup(node_t* ls) {
	node_t* current = ls;
	node_t* tmp = current;
	
	while(current) {
		tmp = current->next;
		free(current);
		current = tmp;
	}
}


/* visits each data element on the list with specified function; for example, if your list were of malloc()ed character strings, you could call

   list_visit(ls, free);
   
to free storage for each element before calling list_cleanup */

void list_visit(node_t* ls, void(*visitor)(void*)) {
	node_t* current = ls;

	while(current) {
		visitor(current->data);
		current = current->next;
	}
}


#ifdef TEST_LLIST
void print_int(void* my_int) {
	int x = (int)my_int;
	printf("%d\n", x);
}

int main(int c, char *v) {
	node_t* ls = NULL;
	int i;
	
	for (i = 0; i < 10; i++) {
		ls = list_append(ls, new_node((void*)i));
	}
	
	for (i = 20; i > 9; i--) {
		ls = list_prepend(ls, new_node((void*)i));
	}
	
	list_visit(ls, print_int);
	
	list_cleanup(ls);
	
	exit(0);
}
#endif /* TEST_LLIST */