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#ifndef STACK_HPP
#define STACK_HPP 1

#include <cassert>
#include <iostream>
#include <utility>

class Stack {
    public:

        Stack() : top(nullptr)
        {
            #ifdef DEBUG
            std::cout << "Stack()" << std::endl;
            #endif
        }

        Stack(const Stack &stack) : top(nullptr)
        {
            #ifdef DEBUG
            std::cout << "Stack(const Stack &)" << std::endl;
            #endif
            copy_elements(stack.top);
        }

        Stack(Stack &&stack) : Stack()
        {
            #ifdef DEBUG
            std::cout << "Stack(Stack &&)" << std::endl;
            #endif
            swap(*this, stack);
        }

        ~Stack()
        {
            #ifdef DEBUG
            std::cout << "~Stack()" << std::endl;
            #endif
            while (!empty()) {
                pop();
            }
        }

        friend void swap(Stack& s1, Stack& s2)
        {
            std::swap(s1.top, s2.top);
        }

        Stack &operator=(Stack stack)
        {
            swap(*this, stack);
            return *this;
        }

        bool empty() const
        {
            return !top;
        }

        void push(double value)
        {
            Element *add = new Element;
            add->last    = top;
            add->value   = value;
            top  = add;
        }

        double pop()
        {
            assert(!empty());

            Element *remove = top;
            top             = remove->last;
            double value    = remove->value;
            delete remove;
            return value;
        }

        // not asked: just for testing
        void print(const char *txt = 0const
        {
            if (txt) {
                std::cout << txt << std::endl;
            } else {
                std::cout << "Stack contains:" << std::endl;
            }
            print_elements(top);
            std::cout << std::endl << std::endl;
        }

    private:

        struct Element {
            Element     *last;
            double      value;
        };

        void copy_elements(const Element *element)
        {
            if (element) {
                copy_elements(element->last);
                push(element->value);
            }
        }

        // not asked: just for testing
        void print_elements(const Element *element) const
        {
            if (element) {
                print_elements(element->last);
                std::cout << element->value << "   ";
            }
        }

        Element     *top;
};

#endif // STACK_HPP