Stack implementation using arrays

Please comment on the same. How can it be improved?

Specific improvements I am looking for:

• Memory leaks

• C++ style

• Making code run faster

• RAII

#include
#include

template 
class Stack {
private:
    T* array_;
    int length_;
    T* last_;
    void expandArray();

public:
    Stack(int length = 8) :
        array_(new T[length]),
        length_(length),
        last_(array_)
    {}

    Stack& push(const T&);
    Stack& pop();
};

template
void Stack::expandArray() {
    T* array_temp = new T[length_ 
Stack& Stack::push(const T& data) {
    if (last_ == (array_ + length_ - 1)) {
        expandArray();
    }
    last_[0] = data;
    last_++;
    std::cout 
Stack& Stack::pop() {
    if(array_ != last_) {
        last_--;
        std::cout  s;
    s.push(std::string("a"))
     .push(std::string("b"))
     .push(std::string("c"))
     .push(std::string("d"));
    s.pop().pop().pop().pop().pop();
}

First of all, I would specify that your stack is using a "dynamically allocated array", as opposed to just an array, as I at first expected a C array when looking at the title. That varies from person to person, though.

On to more important things:

• I would not print anything in the stack functions. If someone wants information on what they're pushing and popping, let them do it themselves.

• You seem to be missing a peek function.

• Either throw an exception or add an assert to pop for the array_ == last_ case.

• length_ should actually be called capacity_.

• expandArray may leak memory if the copy throws. I would use an std::vector internally for this stuff.

• You don't check that length > 0 in the constructor.

• I would not allocate so anything by default.

• You lack all three of a copy constructor, assignment operator, and destructor, so you'll definitely leak memory. You should also have a move constructor and a move assignment operator, but those aren't as critical.

• You provide no way to check whether the stack is empty.

StackExchange Code Review Q#15640, answer score: 11