source: doc/generic_types/evaluation/cpp-stack.h@ c51b5a3

#pragma once

#include <utility>

template<typename T> class stack {
        struct node {
                T value;
                node* next;

                node( T& v ) : value(v), next(nullptr) {}
                node( T&& v, node* n ) : value(std::move(v)), next(n) {}
        };
        
        node* head;

        void copy(const stack<T>& o) {
                node** crnt = &head;
                node* next = o.head;
                while ( next ) {
                        *crnt = new node{ next->value };
                        crnt = &(*crnt)->next;
                        next = next->next;
                }
                *crnt = nullptr;
        }

public:
        void clear() {
                node* next = head;
                while ( next ) {
                        node* crnt = next;
                        next = crnt->next;
                        delete crnt;
                }
        }

        stack() : head(nullptr) {}

        stack(const stack<T>& o) { copy(o); }

        stack(stack<T>&& o) : head(o.head) { o.head = nullptr; }

        ~stack() { clear(); }

        stack& operator= (const stack<T>& o) {
                if ( this == &o ) return *this;
                clear();
                copy(o);
                return *this;if ( this == &o ) return *this;
        }

        stack& operator= (stack<T>&& o) {
                if ( this == &o ) return *this;
                head = o.head;
                o.head = nullptr;
                return *this;
        }

        bool empty() const {
                return head == nullptr;
        }

        void push(T&& value) {
                head = new node{ std::move(value), head };
        }

        T pop() {
                node* n = head;
                head = n->next;
                T x = std::move(n->value);
                delete n;
                return x;
        }
};