unique_ptr<widget> in a list, modify them

widgetlist.cpp

// Example program
#include <iostream>
#include <string>
#include <list>
#include <algorithm>

#include <memory>

typedef struct widget {
    size_t i;
    widget(const size_t i_);
    ~widget();
} widget;

widget::widget(const size_t i_) : i(i_) {
    std::cout << "widget " << i << " is born at " << this << std::endl;
};

widget::~widget(){
    std::cout << "widget " << i << " is dying at " << this << std::endl;
};

using widget_ptr = std::unique_ptr<widget>;

static std::list<widget_ptr> widget_pop;

void addone2widget(widget_ptr& wd){
    wd->i++;
}

int main()
{
    
    widget_pop.emplace_back(std::make_unique<widget>(0));
    widget_pop.emplace_back(std::make_unique<widget>(1));
    widget_pop.emplace_back(std::make_unique<widget>(2));
    widget_pop.emplace_back(std::make_unique<widget>(3));
    widget_pop.emplace_back(std::make_unique<widget>(4));
    
    for(auto& w : widget_pop){
        addone2widget(w);
    }
    
            for(auto& w : widget_pop){
        std::cout << "widget " << w->i << " says hi! \n";
    }
    
        std::cout << "going ot get rid of some widgets" << std::endl;
    
    auto new_end = std::remove_if(widget_pop.begin(), widget_pop.end(),
                              [](const widget_ptr& wd)
                              { return (wd->i == 2) || (wd->i == 4); });

widget_pop.erase(new_end, widget_pop.end());
    
        for(auto& w : widget_pop){
        std::cout << "widget " << w->i << " says hi! \n";
    }

    std::cout << "done removing" << std::endl;

}