#include <sstream>
#include <typeinfo>

class any {
    struct type_eraser {
        virtual ~type_eraser() = default;
        virtual const std::type_info& info() = 0;
    } *_ptr;

    template<typename T>
    struct type_holder : type_eraser {
        T value;
        virtual const std::type_info& info() override {
            return typeid(T);
        }
    };

public:
    any()
        : _ptr(nullptr)
    {}

    template<typename T>
    any(const T& val) {
        _ptr = new type_holder<T>;
        static_cast<type_holder<T>*>(_ptr)->value = val;
    }

    ~any() {
        reset();
    }

    void reset() {
        if (_ptr) {
            delete _ptr;
            _ptr = nullptr;
        }
    }

    const std::type_info& type() {
        if (_ptr)
            return _ptr->info();
        else
            return typeid(void);
    }

    template<typename T>
    T unbox() {
        if (typeid(T) == type()) {
            return static_cast<type_holder<T>*>(_ptr)->value;
        }
        else {
            std::stringstream msg_str;
            msg_str << "Failed to unbox from type '" << type().name() << "' to type '" << typeid(T).name() << '\'';
            throw std::runtime_error{msg_str.str()};
        }
    }
};