added pop, need testing

include/stack.h

@@ -3,6 +3,7 @@
 
 #include <cstdint>
 #include <expected>
+#include <format>
 #include <new>
 
 #define DEFAULT_STACK_SIZE 4
@@ -14,6 +15,7 @@ enum class StackErr {
 };
 
 template<typename T>
+requires std::formattable<T, char>
 class Stack {
 private:
     uint64_t len;
@@ -34,6 +36,7 @@ public:
 };
 
 template <typename T>
+requires std::formattable<T, char>
 Stack<T>::Stack() {
     Stack<T> new_stack;
     new_stack.data = new T[DEFAULT_STACK_SIZE];
@@ -43,11 +46,13 @@ Stack<T>::Stack() {
 }
 
 template <typename T>
+requires std::formattable<T, char>
 Stack<T>::~Stack() {
     delete[] this->data;
 }
 
 template <typename T>
+requires std::formattable<T, char>
 StackErr Stack<T>::push(T value) {
     // If not enough space allocate more space
     if (this->len >= this->cap) {
@@ -74,4 +79,34 @@ StackErr Stack<T>::push(T value) {
     return StackErr::ok;
 }
 
+template <typename T>
+requires std::formattable<T, char>
+std::expected<T, StackErr> Stack<T>::pop() {
+    if (this->len == 0) {
+        return std::unexpected(StackErr::empty);
+    }
+
+    T return_val = this->data[this->len - 1];
+
+    if (this->cap / 4 > this->len) {
+        uint64_t new_capacity = this->cap / 2;
+        T *tmp;
+
+        try {
+            tmp = new T[new_capacity];
+        } catch (const std::bad_alloc& e) {
+            return std::unexpected(StackErr::bad_alloc);
+        }
+
+        for (int i = 0; i < this->len; i++) {
+            tmp[i] = this->data[i];
+        }
+
+        delete[] this->data;
+        this->data = tmp;
+    }
+
+    return std::expected(return_val);
+}
+
 #endif // !ST