Commit 7c4da6d

@@ -1,7 +1,7 @@
 #include "stack.h"
 #include <stdlib.h>
 
-Node *node_init(int data) {
+Node *node_init(void *data) {
   Node *node = malloc(sizeof(Node));
   node->next = NULL;
   node->data = data;
@@ -18,7 +18,7 @@ int stack_size(Stack *self) {
   if (!self || !self->head)
     return 0;
 
-  int count;
+  int count = 0;
   Node *current = self->head;
   while (current) {
     ++count;
@@ -28,25 +28,25 @@ int stack_size(Stack *self) {
   return count;
 }
 
-int stack_peek(Stack *self) {
+void *stack_peek(Stack *self) {
   if (self->head)
     return self->head->data;
-  return -1;
+  return NULL;
 }
 
-void stack_push(Stack *stack, int data) {
+void stack_push(Stack *stack, void *data) {
   Node *node = node_init(data);
   node->next = stack->head;
   stack->head = node;
 }
 
-int stack_pop(Stack *self) {
+void *stack_pop(Stack *self) {
   if (self->head) {
     Node *tmp = self->head;
-    int data = tmp->data;
+    void *data = tmp->data;
     self->head = self->head->next;
     free(tmp);
     return data;
   }
-  return -1;
+  return NULL;
 }

@@ -1,6 +1,6 @@
 typedef struct node {
   struct node *next;
-  int data;
+  void *data;
 } Node;
 
 typedef struct {
@@ -8,7 +8,7 @@ typedef struct {
 } Stack;
 
 Stack *stack_init();
-int stack_peek(Stack *self);
+void *stack_peek(Stack *self);
 int stack_size(Stack *self);
-void stack_push(Stack *self, int data);
-int stack_pop(Stack *self);
+void stack_push(Stack *self, void *data);
+void *stack_pop(Stack *self);

@@ -9,7 +9,7 @@ AfterEach(Stack) {}
 Ensure(Stack, when_pushing_an_item_on_to_a_stack) {
   Stack *stack = stack_init();
 
-  stack_push(stack, 10);
+  stack_push(stack, (void *)10);
 
   assert_that(stack_size(stack), is_equal_to(1));
   assert_that(stack_peek(stack), is_equal_to(10));
@@ -18,22 +18,36 @@ Ensure(Stack, when_pushing_an_item_on_to_a_stack) {
 Ensure(Stack, when_pushing_multiple_items_on_to_a_stack) {
   Stack *stack = stack_init();
 
-  stack_push(stack, 20);
-  stack_push(stack, 10);
-  stack_push(stack, 50);
+  stack_push(stack, (void *)20);
+  stack_push(stack, (void *)10);
+  stack_push(stack, (void *)50);
 
   assert_that(stack_size(stack), is_equal_to(3));
   assert_that(stack_peek(stack), is_equal_to(50));
 }
 
+Ensure(Stack, when_pushing_a_custom_type_on_to_a_stack) {
+  typedef struct {
+  } Item;
+
+  Stack *stack = stack_init();
+  Item *item = malloc(sizeof(Item));
+
+  stack_push(stack, item);
+
+  assert_that(stack_size(stack), is_equal_to(1));
+  assert_that(stack_peek(stack), is_equal_to(item));
+  assert_that(stack_pop(stack), is_equal_to(item));
+}
+
 Ensure(Stack, when_popping_an_item_off_of_a_stack) {
   Stack *stack = stack_init();
 
-  stack_push(stack, 20);
-  stack_push(stack, 10);
-  stack_push(stack, 50);
+  stack_push(stack, (void *)20);
+  stack_push(stack, (void *)10);
+  stack_push(stack, (void *)50);
 
-  int result = stack_pop(stack);
+  void *result = stack_pop(stack);
 
   assert_that(stack_size(stack), is_equal_to(2));
   assert_that(stack_peek(stack), is_equal_to(10));