/**
 * dstack.c - Implementations of simple stack functions.
 *   Based closely on code taken from section 4.3 of K&R, although
 *   I've removed the precondition checking since error messages
 *   should be passed to the client, rather than to the user.
 */

// +---------+--------------------------------------------------------
// | Headers |
// +---------+

#include <stdio.h>	// For fprintf
#include "dstack.h"


// +-----------+------------------------------------------------------
// | Constants |
// +-----------+

/**
 * The maximum size of the stack.
 */
#define MAXSIZE 8


// +---------+--------------------------------------------------------
// | Globals |
// +---------+

/**
 * The array in which we store values.
 */
double dstack[MAXSIZE];

/**
 * The position in the array that stores the most-recently pushed
 * value.  (When 0, there is nothing on the stack.
 */
int sp = 0;


// +--------------------+---------------------------------------------
// | Exported Functions |
// +--------------------+

void
dpush (double d)
{
  dstack[sp++] = d;
} // dpush

double
dpop (void)
{
  return dstack[--sp];
} // dpop