Please read the pattern matching proposal:

P1371 Pattern Matching
https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2020/p1371r3.pdf

Jens


On 9/10/26 21:05, Jefferson Carpenter via Std-Discussion wrote:
> Hi all,
>
> I'd like to propose some "syntactic sugar" that ties the switch
> statement language feature to the std::variant standard library type.
> The idea is to make the process of visiting a variant much cleaner and
> simpler.
>
> Basically it has to support the following code transformation:
>
> switch (x) { // Assume x is of type std::variant<MyClass, int>
> case (MyClass myclass): { a(myclass); break; }
> case (int n): { b(n); break; }
> }
>
> to the following:
>
> struct Unnamed {
> void operator()(MyClass const& myclass) { a(myclass); }
> void operator()(int const& n) { b(n); }
> };
> Unnamed{}(x);
>
> so that the code jumped to from each case is transformed into a
> function call operator overload. A braced-enclosed code block ending
> in a break statement may be required after each case "label" even when
> there are no variables declared in the body or if fallthrough were
> desired so that the code that must be moved is outlined and easy to
> move.
>
> This could potentially be extended to other non-std::variant types if
> there were a mechanism like std::get, but I haven't explored this at
> all.
>
>
> This would be very useful to me, as I've written a lot of
> programming-language-like programs and use std::variant extensively to
> represent expression trees.
>
> It would make C++ much more viable for programs like this to have the
> code for visitors easier to read and type than calls to std::visit.
>
>
> Warm Regards,
> Jefferson Carpenter