/*--------------------------------------------------------------------*/
/* stack.h (Version 1)                                                */
/* Author: Bob Dondero                                                */
/*--------------------------------------------------------------------*/

#ifndef STACK_INCLUDED
#define STACK_INCLUDED

/* A Stack is a last-in-first-out collection of doubles. */

struct Stack
{
   /* The array in which items are stored. */
   double *pdArray;

   /* The index one beyond the top element. */
   int iTop;

   /* The number of elements in the array. */
   int iPhysLength;
};

struct Stack *Stack_new(void);
/* Return the address of a new Stack. */

void Stack_free(struct Stack *psStack);
/* Free psStack.  Do nothing if psStack is NULL. */

void Stack_push(struct Stack *psStack, double dItem);
/* Push dItem onto *psStack.
   It is a checked runtime error for psStack to be NULL. */

double Stack_top(struct Stack *psStack);
/* Return the top item of *psStack.
   It is a checked runtime error for psStack to be NULL
   or for *psStack to be empty. */

void Stack_pop(struct Stack *psStack);
/* Pop *psStack and discard the popped item.
   It is a checked runtime error for psStack to be NULL
   or for *psStack to be empty. */

int Stack_isEmpty(struct Stack *psStack);
/* Return 1 (TRUE) iff *psStack is empty.
   It is a checked runtime error for psStack to be NULL. */

#endif