#ifndef _STACK_H
#define _STACK_H
#include "types.h"

typedef struct {
  number_t *data;
  index_t  size;
  index_t  sp;
} stack_t;


/*
  Check for possible stack underflow (should normally not happen, in contrast to stack overflow)
*/
#if STACKUNDERFLOWCHECK>0 
#define STACKUNDERFLOW(DS,N,R) if (SEMPTYN(DS,N)) { R->error=ESTACK; return 0; };
#else
#define STACKUNDERFLOW(DS,N,R)
#endif

#define SEMPTY(S)     S->sp==0
#define SFULL(S)      S->sp==S->size
#define SEMPTYN(S,n)  S->sp<n
#define SFULLN(S,n)  (S->sp+n)>S->size
#define POP(S)        S->data[--S->sp]
#define PUSH(S,x)     S->data[S->sp++]=x
#define NTH(S,n)      S->data[S->sp-n]

stack_t * StackAllocate(int size);
void StackCopy(stack_t *src, stack_t *dst);
void StackInit(stack_t *S,int size,number_t *data);
void StackReset(stack_t *S);

#endif