stack.c

Multi-module programs and MAKE

#include <stdio.h>
#include "stack.h"
#define MAXVAL 100                 /* maximum depth of val stack */

/* even better, we could make the following two defines "static"
   and thus hide these data structures from the rest of the sources */
int sp = 0;                        /* next free stack position */
int val[MAXVAL];                   /* value stack */

/* note: "f" is a funny name for a generic int--"i" would be better */

/* push: push f onto value stack */
void push(int f)
{
    if (sp < MAXVAL)
	val[sp++] = f;
    else
	printf("error: stack full, can't push %d\n", f);
}

/* pop: pop and return top value from stack */

int pop(void)
{
    if (sp > 0)
	return val[--sp];
    else{
	printf("error: stack empty\n");
	return 0;
    }
}