What is wrong if line 79 in Listing ImprovedStack.h is replaced by delete old;LISTING Impr...

What is wrong if line 79 in Listing ImprovedStack.h is replaced by delete old;

LISTING ImprovedStack.h

1 #ifndef IMPROVEDSTACK_H2 #define IMPROVEDSTACK_H34 template <typename T>5 class Stack6 {7 public: 8  Stack();9  Stack(const Stack&);10 ~Stack();11 bool empty() const ;12 T peek() const;13 void push(T value);14 T pop();15 int getSize() const;1617 private: 18  T* elements;19  int size;20  int capacity;21  void ensureCapacity();22 };2324 template <typename T>25 Stack::Stack(): size(0), capacity(16)26 {27 elements = new T[capacity];28 }2930 template 31 Stack::Stack(const Stack& stack)32 {33 elements = new T[stack.capacity];34 size = stack.size;35 capacity = stack.capacity;36 for (int i = 0 ; i < size; i++)37 {38  elements[i] = stack.elements[i];39 }40 }4142 template 43 Stack::~Stack()44 {45 delete [] elements;46 }4748 template 49 bool Stack::empty() const50 {51 return size == 0 ;52 }5354 template 55 T Stack::peek() const 56 {57 return elements[size - 1];58 }5960 template 61 void Stack::push(T value)62 {63 ensureCapacity();64 elements[size++] = value;65 }6667template 68 void Stack::ensureCapacity()69 {70 if (size >= capacity)71 {72 T* old = elements;73 capacity = 2 * size;74 elements = new T[size * 2];7576 for (int i = 0 ; i < size; i++)77 elements[i] = old[i];7879 delete [] old;80 }81 }8283template 84 T Stack::pop()85 {86 return elements[−−size];87 }8889template 90 int Stack::getSize() const91 {92 return size;93 }9495 #endif