/*--------------------------------------------------------------------*/
/* stack.h (Version 2)                                                */
/* Author: Bob Dondero                                                */
/*--------------------------------------------------------------------*/

#ifndef STACK_INCLUDED
#define STACK_INCLUDED

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

struct Stack *Stack_new(void);
/* Return 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