What do I do with the error in implementing the stack? - c

Question

#include <stdio.h>
#define stack 100
void push(int x);
int st[stack];
int top = -1;
int IsEmpty()
{
if (top < 0)
return false;
else
return true;
}
int Isfull()
{
if (top >= stack - 1)
return true;
else
return false;
}
void push(int x)
{
if (Isfull() == true)
printf("stack is full");
else
st[++top]=x;
}
int pop() {
if (IsEmpty() == true)
printf("stack is empty.");
else
return stack[top--];/// There is an error in this part. (expression must have pointer-to-object type)
}
int main()
{
push(3);
}
int pop() {
if (IsEmpty() == true)
printf("stack is empty.");
else
return stack[top--];There is an error in this part. (expression must have pointer-to-object type)
expression must have pointer-to-object type
Stack is being implemented as an array And then there's this error.
What should I do?
Is this a Syntex error? Tell me the wrong part.
and If there is anything else that needs to be corrected, please let me know.
C language is difficult. Have you all experienced this kind of error?

Answer 1

return stack[top--]; same as return 100[top--];.
I suspect you wanted return st[top--];
Use a different name for the stack size too to avoid such name collisions.
// #define stack 100
#define STACK_SIZE 100

Answer 2

I see 3 problems:
A simple typo:
return stack[top--]; ==> return st[top--];
stack is the array size but your array is named st
Missing return value
This code has no return value when the stack is empty.
int pop() {
if (IsEmpty() == true)
printf("stack is empty.");
// No return value here
else
Even if the stack is empty you must return a value. So you need to handle that in another way. One option is to return a dummy value (e.g. zero), another is to exit the program or change the pop-function signature so that it can tell whether it was succesful. For instance:
// Option 1: Return dummy value
int pop() {
if (IsEmpty()) return 0;
return stack[top--];
}
// Option 2: Exit program
int pop() {
if (IsEmpty()) exit(1);
return stack[top--];
}
// Option 3: Let the function tell whether is was a success
int pop(int* data) {
if (IsEmpty()) return 0;
*data = stack[top--];
return 1;
}
The last pop-function returns 1 on success - zero otherwise.
Wrong logic
This function:
int IsEmpty()
{
if (top < 0)
return false;
else
return true;
}
is wrong. Change it to:
int IsEmpty()
{
if (top < 0)
return true;
else
return false;
}
or more simple
int IsEmpty()
{
return (top < 0);
}