Double linked list

double_linked_list.c

#include <stdlib.h>
#include <stdio.h>
/**
* please put the stuff that needs to be in .h
* file in the header file. anyway, that shit 
* serves educational purposes and shall not be 
* used anywhere. the purpose of that shit is
* to demonstrate the concept of iterators in C99
* DELETEME: test of how does gist time line behave
*/

struct double_linked_node 
{
	char data;
	struct double_linked_node *prev, *next;
};

struct double_linked_list 
{
	struct double_linked_node *first, *last;
};

struct double_linked_node dln_new_node (char arg_c) 
{
	struct double_linked_node new_node;
	new_node.data = arg_c;
	new_node.prev = new_node.next = NULL;
	return new_node;
}

struct double_linked_list dln_new_list () {
	struct double_linked_list new;
	new.first = new.last = NULL;
	return new;
}

void dln_append ( struct double_linked_node *arg_c, 
		struct double_linked_list *arg_list ) 
{
	(*arg_c).next = NULL;
	(*arg_c).prev = (*arg_list).last;
	if ((*arg_list).last != NULL) 
		(*(*arg_list).last).next = arg_c;
	
	if ((*arg_list).first == NULL) 
		(*arg_list).first = arg_c;

	(*arg_list).last = arg_c;
}

/**
* 
* Iterators :3
*
*/

// my favorite type of C99 iter
void dln_traverse_forward ( const struct double_linked_list arg_list,
		void (*callback)(const struct double_linked_node *) ) 
{
	printf("traversing double_linked_list forward\n");
	struct double_linked_node *curr_node = arg_list.first;
	//callback(arg_list.first);
	while (curr_node != NULL){
		callback(curr_node);
		curr_node = (*curr_node).next;
	};
	//callback(arg_list.last);
	return;
}

// iter to be used in for loop
struct double_linked_node *dln_fwd_first ( const struct double_linked_list l)
{
	return l.first;
}
struct double_linked_node *dln_fwd_next ( const struct double_linked_node *n )
{
	return (*n).next;
}
int dln_fwd_done ( const struct double_linked_node *n )
{
	return n == NULL;
}

//


void dln_clb_example ( const struct double_linked_node *arg_node) 
{
	printf("* %c \n", (*arg_node).data);
	return;
}

int main (void) {
	struct double_linked_list peka = dln_new_list();
	struct double_linked_node l = dln_new_node('l');
	struct double_linked_node y = dln_new_node('y');
	struct double_linked_node a = dln_new_node('a');
	struct double_linked_node m = dln_new_node('m');
	
	dln_append(&l, &peka);
	dln_append(&y, &peka);
	dln_append(&a, &peka);
	dln_append(&m, &peka);
	
	// foreach iterator
	dln_traverse_forward(peka, dln_clb_example);

	// first/next/done iterator
	for 
	(
		struct double_linked_node* i = dln_fwd_first(peka);
		!(dln_fwd_done(i));
		i = dln_fwd_next(i)
	)
	{
		printf("** %c \n", (*i).data);
	}

	return 0;
}