#ifndef __PF_STACK__
#define __PF_STACK__

/**
   @file stack.h
   @brief Basic stack operations

   All the pf_stack_ functions perform reference count management. 
   As opposed to pf_list_ and pf_tree_ operations, which work on the list/tree structure only.

   A stack is treated as a tree (all embedded lists are branches), and all data is owned
   by the stack. Note that if you create objects that are not referenced on the stacks
   (return/data/dictionary stacks), you explicitly need to manage them yourself.

*/

void pf_stack_free(pf_stack_t *s);
void pf_stack_clear(pf_stack_t *s);

/* forth words. not all the words in forth.c are declared here.
   if you need more (i.e. for extension modules), this is the place to add declarations. */

pf_error_t pf_stack_drop(pf_stack_t *s);
pf_error_t pf_stack_swap(pf_stack_t *s);

/* some util stuff */
pf_stack_t *pf_stack_new(void);

void pf_stack_free(pf_stack_t *s);
void pf_stack_clear(pf_stack_t *s);


static inline pf_error_t pf_check_atom(pf_atom_t *s, int n){
    while (n--) 
	if (!(s = pf_atom_next(s))) return e_underflow;
    return e_ok;
}

/* stack type checking macros */
#define PF_STACK_CHECKN(s, n)           if (pf_list_elements(s) < n) return e_underflow

#define PF_STACK_CHECK1T(s, t0)         if (pf_atom_type(PF_LIST_ATOM_0(s)) != t0) return e_type
#define PF_STACK_CHECK2T(s, t0, t1)     PF_STACK_CHECK1T(s, t0); if(pf_atom_type(PF_LIST_ATOM_1(s)) != t1) return e_type
#define PF_STACK_CHECK3T(s, t0, t1, t2) PF_STACK_CHECK2T(s, t0, t1); if(pf_atom_type(PF_LIST_ATOM_2(s)) != t2) return e_type
#define PF_STACK_CHECK4T(s, t0, t1, t2, t3) PF_STACK_CHECK3T(s, t0, t1, t2); if(pf_atom_type(PF_LIST_ATOM_3(s)) != t3) return e_type

#define PF_STACK_CHECK1(s, t0)          PF_STACK_CHECKN(s, 1); PF_STACK_CHECK1T(s, t0)
#define PF_STACK_CHECK2(s, t0, t1)      PF_STACK_CHECKN(s, 2); PF_STACK_CHECK2T(s, t0, t1)
#define PF_STACK_CHECK3(s, t0, t1, t2)  PF_STACK_CHECKN(s, 3); PF_STACK_CHECK3T(s, t0, t1, t2)
#define PF_STACK_CHECK4(s, t0, t1, t2, t3)  PF_STACK_CHECKN(s, 4); PF_STACK_CHECK4T(s, t0, t1, t2, t3)


/* atom pointer checks */
#define PF_ATOM_CHECK_READ(a)  if (!a || pf_atom_stale(a)) return e_pointer
//#define PF_ATOM_CHECK_WRITE(a) PF_ATOM_CHECK_READ(a); if (!(a->flags & PF_FORTH_ATOM_FLAG_WRITABLE)) return e_access







#endif