simple stack

[paulmedic555]

Hi all i am learning C now and i want to make a program that for a simple stack (an integer array) i will insert elements (integers) in the stack until it will be full or remove them until it will be empty.Here is my code:

#define N 2
int stack[N];
int head=0;

#include<stdio.h>
void push(int);
int pop(void);

int main()
{
	int s,k;

	do
	{
		printf("Give your selection\n");
		printf("1.Push\n");
		printf("2.Pop\n");
		printf("3.Finish\n");
		scanf("%d",&s);
		switch(s)
		{
			case 1:
			{
				printf("give an element to push in the stack:\n");
				r=scanf("%d",&k);
				if (r==1)
					push(k);
				else
				{
					printf("You don't give a valid number");
					return 0;
				}
				break;
			}
			case 2:
			{
				pop();
				break;
			}
		}
	}
	while(s!=3);

}

void push(int e)
{
	if (head<N)
		stack[head++]=e;
	else
		printf("STACK IS FULL\n");
}


int pop(void)
{
	if(head>0)
		return stack[--head];
	else
		printf("STACK IS EMPTY\n");
}

My problem is that here i declare the array and the index of the stack(head) as global variables but when i try to declare them as local variables in main and pass them to push and pop functions i can't get it to work.Any ideas?

[Happy_Reaper]

Ok this is probably because you're not passing your variables by reference to you function, and therefore head++ increments the copy of head that you're sending to the function, so head(in main) always stays at 0.

[vart]

by reference

because it is c - not a reference but pointers should be used...

I think the better way is to use a struct

typedef struct
{
   int items[N];
   unsigned int head=0;
}stack;

in main declare the variable of this type

stack myStack;

and pass the pointer to it in the push/pop functions

push(&myStack, newValue);

value = pop(&myStack);

[Happy_Reaper]

because it is c - not a reference but pointers should be used...

Agreed. But from what I remember, sending a variable to a function using a pointer is what's called passing the argument by reference. When you don't use a pointer, it's passing the argument by value.

And I agree that ideally you'd want a structure for the stack, but if the OP wants to stick with his array, those small changes will get him what he desires.