Stack Undo

A stack keeps the most recent item on top, which is the same access pattern used by simple undo histories.

stack_undo.cpp

#include <iostream>
#include <stack>
#include <string>

int main() {
    std::string latest = ;

    std::stack<std::string> undo;
    undo.push("open");
    undo.push(latest);

    std::string next = undo.top();
    undo.pop();
    int remaining = static_cast<int>(undo.size());

    std::cout << "next=" << next << std::endl;
    std::cout << "remaining=" << remaining << std::endl;
    return 0;
}

#include <iostream>
#include <stack>
#include <string>

int main() {
    std::string latest = ;

    std::stack<std::string> undo;
    undo.push("open");
    undo.push(latest);

    std::string next = undo.top();
    undo.pop();
    int remaining = static_cast<int>(undo.size());

    std::cout << "next=" << next << std::endl;
    std::cout << "remaining=" << remaining << std::endl;
    return 0;
}

#include <iostream>
#include <stack>
#include <string>

int main() {
    std::string latest = ;

    std::stack<std::string> undo;
    undo.push("open");
    undo.push(latest);

    std::string next = undo.top();
    undo.pop();
    int remaining = static_cast<int>(undo.size());

    std::cout << "next=" << next << std::endl;
    std::cout << "remaining=" << remaining << std::endl;
    return 0;
}

stack A `std::stack` exposes only the top item and follows last-in, first-out order.

undo Undo histories use the newest action first, so a stack is a natural model.