Checkpoint at the end of part 1

part1-recap.c

/* int_stack.h */

#include <stdbool.h>

typedef struct int_stack IntStack;

IntStack* new_stack();
void push_to_stack(IntStack* stack, int value);
int pop_stack(IntStack* stack);
int peek_stack(IntStack* stack);
bool is_empty_stack(IntStack* stack);
void delete_stack(IntStack** stack);

/* main.c */
#include "int_stack.h"
#include <stdio.h>

int main()
{
    IntStack* stack = new_stack();
    for (int i = 5; i > 0; i--) {
        push_to_stack(stack, i);
    }
    printf("At the top of the stack is `%d`\n\n", peek_stack(stack));
    while (!is_empty_stack(stack)) {
        printf("`%d` was popped from the stack\n", pop_stack(stack));
    }
    delete_stack(&stack);
    return 0;
}

/* int_stack.c */
#include "int_stack.h"
#include <stdlib.h>

typedef struct int_node IntNode;
struct int_stack {
    IntNode* top;
};

IntStack* new_stack()
{
    IntStack* stack = malloc(sizeof (IntStack));
    stack->top = NULL;
    return stack;
}

struct int_node {
    int  value;
    struct int_node* next;
};

void push_to_stack(IntStack* stack, int value)
{
    IntNode* pushed = malloc(sizeof (IntNode));
    pushed->value = value;
    pushed->next = stack->top;
    stack->top = pushed;
}

int pop_stack(IntStack* stack)
{
    IntNode* new_top = stack->top->next;
    int popped = stack->top->value;
    free(stack->top);
    stack->top = new_top;
    return popped;
}

int peek_stack(IntStack* stack)
{
    return stack->top->value;
}

bool is_empty_stack(IntStack* stack)
{
    return !stack->top;
}

void delete_stack(IntStack** stack)
{
    while (!is_empty_stack(*stack)) {
        pop_stack(*stack);
    }
    free(*stack); *stack = NULL;
}