online compiler and debugger for c/c++

#include <iostream> #include <variant> /// This version does not work as I expect. /// /// Expected program output: /// A /// B /// OTHER /// OTHER /// /// Actual program output: /// OTHER /// OTHER /// OTHER /// OTHER /// Delta from working version of program: /// 1. my_visit() only has the const method overload, the non-const version has been commented out. template<class... Ts> struct overloaded : Ts... { using Ts::operator()...; }; template<class... Ts> overloaded(Ts...) -> overloaded<Ts...>; struct A {}; struct B {}; struct C {}; struct D {}; using V = std::variant<A, B, C, D>; class MyVisitor { V v_; public: MyVisitor(V &&v) : v_(std::move(v)) {} /// template <typename ...Args> /// decltype(auto) my_visit(Args&&... args) /// { /// return std::visit(overloaded{std::forward<Args>(args)...}, v_); /// } template <typename ...Args> decltype(auto) my_visit(Args&&... args) const { return std::visit(overloaded{std::forward<Args>(args)...}, v_); } }; int main() { auto const print_a = [](A&) { std::cerr << "A\n"; }; auto const print_b = [](B&) { std::cerr << "B\n"; }; auto const print_o = [](auto&) { std::cerr << "OTHER\n"; }; { // this prints "A" V v{A{}}; MyVisitor visitor{std::move(v)}; visitor.my_visit(print_a, print_b, print_o); } { // this prints "B" V v{B{}}; MyVisitor visitor{std::move(v)}; visitor.my_visit(print_a, print_b, print_o); } { // this prints "OTHER" V v{C{}}; MyVisitor visitor{std::move(v)}; visitor.my_visit(print_a, print_b, print_o); } { // this prints "OTHER" V v{D{}}; MyVisitor visitor{std::move(v)}; visitor.my_visit(print_a, print_b, print_o); } return 0; }