First what is wrong with the existing suggestions?

Here you have a comparison of three proposals:

https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2025/p2688r5.html#matching-strings

Many languages call their "switch" differently.

You still have not specified, whether you suggest that the compiler can assume

 - the given string is one of the options or

 - the given string can be any string

 - the given string can be any string only if a default case is provided

Depending on it, those shorter hash solutions or comparing the first few characters would work or not.

Normally switch is a simple function / logic. If it now could compare more complex objects, this should be clearly defined.

All other programming languages allowing switch (or which name they chose) to do string comparisons, do a full (non-optimized to the selection) comparison, as if you do a chain of if/else.

If this is what you also propose, then perhaps you should extend it to any custom type, too. Why should strings be something special?

MyObject o(42);

...

switch (o) {

case o2:

    ...

    break;

case MyObject(3):

    ...

    break;

case MyObject(5):

    ...

    break;

default:

    ...

}

-----Ursprüngliche Nachricht-----
Von: Zhao YunShan via Std-Proposals <std-proposals@lists.isocpp.org>
Gesendet: Mi 21.05.2025 04:15
Betreff: Re: [std-proposals] A draft for modern switch
An: Nikolay Mihaylov <nmmm@nmmm.nu>;
CC: Zhao YunShan <dou1984@163.com>; std-proposals@lists.isocpp.org;

 

switch is a concept familiar to all programmers. Most languages use switch with strings, including JS, Golang, PHP, etc.
match seems a bit unusual in comparison.

 

Indeed, using a constexpr hash function can construct a perfect hash, but my idea is to have the compiler handle this task rather than doing it manually myself.

 

 

Regards