Stack implementation without using pointers

Question

I need to implement a very basic stack data structure for keeping integers in C without using pointers. Is this possible using only arrays? Simple pseudo code would be highly appreciated.

Edit: I'm using a model checking tool called UPPAAL that supports the basic functionalities of C and I need to use a recursive function which UPPAAL doesn't support. I thought about implementing the recursion using my own stack because UPPAAL doesn't support pointers. Any better ideas?

Why are you allowed to use arrays but not pointers? They are fundamentally the same thing. — Kendall Frey
– Kendall Frey, Commented Jul 28, 2012 at 18:53
Is the restriction against pointers a restriction of the assignment or because you are unsure about using them yourself? — Steven Fines
– Steven Fines, Commented Jul 28, 2012 at 18:55
Smells like homework to me. I can't imagine another scenario which would disallow the use of pointers. — Ed Swangren
– Ed Swangren, Commented Jul 28, 2012 at 19:00
Then why do you have a "no pointer" requirement? That doesn't seem... sane... in the context of non-academic code. — Ed Swangren
– Ed Swangren, Commented Jul 28, 2012 at 19:30

Kerrek SB · Accepted Answer · 2012-08-03 21:45:47Z

3

Assuming that you're allowed to make one dynamic allocation for the entire structure (which you must, one way or another), you can just use integers for an offset:

unsigned int capacity = 100;
unsigned int top      = 0;

int * buf = malloc(sizeof(int) * capacity);

// push:
buf[top++] = n;

// pop:
int value = buf[--top];

// empty:
int is_empty = (top == 0);

// increase capacity:
if (top == capacity)
{
    int * tmp = realloc(buf, capacity * 2 * sizeof(int));
    if (!tmp) { /* out of memory, die */ }
    buf = tmp;
    capacity *= 2;
}

// destroy
free(buf);

This code is just for exposition; in your implementation you would obviously check for overflow and underflow.

edited Aug 3, 2012 at 21:45

answered Jul 28, 2012 at 18:57

Kerrek SB

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1 Comment

BLUEPIXY Over a year ago

push execute buf[top++]=n, after pop execute value=buf[top--] value is not n, value is undefined!

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