Using coroutines we can say something like:

auto f() -> result<int, std::string>
{
    return "Error!";
}

auto g() -> result<int, std::string>
{
    return 5;
}

auto compute() -> result<int, std::string>
{
    int const a = co_await f();
    int const b = co_await g();

    co_return a + b;
}

I think there's only two possible reactions to this, no in-between:

• WTF is this?
• Such a shame there is no direct support from the language for something like this

There is a shell.nix that gives you an environment with all the stuff needed to run this "project"(though you don't need nix, it's just convenient to use). If you have nix you can:

nix-shell

./scripts/build.sh

And then in build/src/ you can run ./cpp-monads.

Most of this was inspired from here and here.