advanced patterns in C++20 when using std::variant with visitor pattern and lambdas
I'm integrating two systems and I've been struggling with this for a few days now and could really use some help. I'm integrating two systems and I'm working with unexpected behavior when trying to use `std::variant` with a visitor pattern in C++20. I'm trying to create a simple type-safe way to handle different types stored in a `std::variant` using lambdas as visitors. However, when I run my code, it seems to always invoke the first alternative, regardless of the type I provide to the `std::visit` function. Here’s a simplified version of my code: ```cpp #include <variant> #include <iostream> #include <string> struct Visitor { void operator()(int i) const { std::cout << "Integer: " << i << '\n'; } void operator()(const std::string& str) const { std::cout << "String: " << str << '\n'; } }; int main() { std::variant<int, std::string> v; v = 42; std::visit(Visitor{}, v); v = "Hello, World!"; std::visit(Visitor{}, v); return 0; } ``` When I execute this code, I expect to see "Integer: 42" followed by "String: Hello, World!". However, I'm only seeing "Integer: 42" printed twice. I’ve checked that the variant is indeed being assigned the correct types, but the visitor seems to be exploring on the first overload. I've tried using `std::monostate` to check the state of the variant before visiting, but it doesn’t seem to solve the question. Is there something I'm missing here about how the visitor pattern works with `std::variant` in C++20? Any insights or suggestions would be greatly appreciated! Any ideas what could be causing this? Cheers for any assistance! Thanks, I really appreciate it!