#ifndef LIFO
#define LIFO

// opaque type for a queue object
typedef struct lrec * lifo;

// returns a new queue object
lifo Lnew();

// add an item to the queue
int Ladd(lifo, void *data);

// remove an item from the queue
void * Lremove(lifo);

// return the head item of the queue
void * Lshow(lifo);

// move the head item to the tail of the queue
// and return the new head item
int Lfree(lifo);

#define ENOMEM		1 // not enough memory to complete the operation
#define EBADL		2 // argument is not a queue
#define ENODATA	3 // no data is available
#define EUNKNOWN	4 // any other error

#endif