Writing a push and pop in c

Question

Original Q: I\'m trying to create this calculator in C for a project. I got the math functions working, but not I am stuck on how to handle the push an pop. Can somebody help me

Answer 1

//Validation sample code of behavior

#include 
#include 
#include 
#include 

#if 0
 #include "stack.h"
 #include "debug.h"
#else
 typedef char* stack_item;
#endif

#define DEFAULT_CAPACITY 16

struct stack {
   size_t capacity;
   size_t size;
   stack_item *data;
};

typedef struct stack stack;

stack *Stack(void){
    stack *s = malloc(sizeof(stack));
    s->capacity = DEFAULT_CAPACITY;
    s->size = 0;
    s->data = malloc(s->capacity * sizeof(stack_item));
    return s;
}

int full_stack(stack *this){
    return this->capacity == this->size;
}

int empty_stack(stack *this){
    return this->size == 0;
}

void realloc_stack(stack *this){
    this->capacity += DEFAULT_CAPACITY;
    this->data = realloc(this->data, this->capacity*sizeof(stack_item));
}

void push_stack (stack *this, stack_item item) {
    if (full_stack (this))
        realloc_stack (this);  
    this->data[this->size++]=item;
}

stack_item pop_stack (stack *this) {
    assert (!empty_stack (this)); 
    if(this->data == NULL){
        fprintf(stderr, "fail");
        exit(1);//Maybe malloc or realloc
    }
    return this->data[--(this->size)];
}

int main(void){
    stack *s = Stack();
    push_stack(s, "sin");
    push_stack(s, "+");
    push_stack(s, "cos");
    while(!empty_stack(s)){
        puts(pop_stack(s));
    }
    //Stack_(s);//call destructor
    return 0;
}