Introducing function pointers

step4-func-pointers.c

/* int_stack.h */

typedef struct int_stack IntStack;
struct int_stack {
    void (*push)(IntStack* this, int value);
    int (*pop)(IntStack* this);
    int (*peek)(IntStack* this);
    bool (*isEmpty)(IntStack* this);
    void (*delete)(IntStack** this);
};

IntStack* new_stack();

/* main.c */

#include "int_stack.h"
#include <stdio.h>

int main()
{
    IntStack* stack = new_stack();
    for (int i = 5; i > 0; i--) {
        stack->push(stack, i);
    }
    printf("At the top of the stack is `%d`\n\n", stack->peek(stack));
    while (!stack->isEmpty(stack)) {
        printf("`%d` was popped from the stack\n", stack->pop(stack));
    }
    stack->delete(&stack);
    return 0;
}