On Thursday, May 22nd, 2025 at 1:07 PM, Jeremy Rifkin via Std-Proposals <std-proposals_at_[hidden]> wrote:

> > Wow, if you believe that C++ must care> about performance, then you may want
> > to consider supporting a `switch` that
> > tests strings!
>

> There is no optimization that is unique to switch. Compilers optimize if-else chains just fine.


I want to write

  switch (foo()) {
    case "old-label":
      migrate();
    case "new-label":
      arg &= flag;
      work1(arg);
      break;
    case "second-case":
      work2(arg);
  }

Please show me how to express this in if...else,
and which compiler optimizes it fine.

--
Zhihao Yuan, ID lichray
The best way to predict the future is to invent it.
_______________________________________________
> Jeremy
> 
> 
> On Thu, May 22, 2025 at 1:45 PM Zhihao Yuan via Std-Proposals <std-proposals_at_[hidden]> wrote:
> 
> > On Thursday, May 22nd, 2025 at 10:53 AM, Nikolay Mihaylov via Std-Proposals <std-proposals_at_[hidden]> wrote:
> > 
> > > My 5 cents again :)
> > > 
> > > I am strongly against modifying switch in this way :)
> > > C++ is C and C++, is not Javascript or PHP where nobody cares about performance.
> > 
> > 
> > Wow, if you believe that C++ must care
> > about performance, then you may want
> > to consider supporting a `switch` that
> > tests strings! What a compiler can do to
> > optimize a pattern matching that tests
> > strings but simulates fall-through between
> > the cases?
> > 
> > --
> > Zhihao Yuan, ID lichray
> > The best way to predict the future is to invent it.
> > _______________________________________________
> > 
> > 
> > > 
> > > This is exactly why match were proposed.
> > > 
> > > On Wed, May 21, 2025 at 4:56 PM Jason McKesson via Std-Proposals <std-proposals_at_[hidden]> wrote:
> > > 
> > > > On Wed, May 21, 2025 at 3:34 AM Filip via Std-Proposals
> > > > <std-proposals_at_[hidden]> wrote:
> > > > >
> > > > > I agree, it seems like a better idea to have switch in non constexpr context available, to act like a nicer option acting like if else.
> > > > >
> > > > > Maybe I’m missing the key functionality of match, but it looks like a different syntax for something that we already have.
> > > > >
> > > > > I agree that assignment with match looks like a good idea, why wouldn’t we add that to the switch statement?
> > > > 
> > > > Because we're getting pattern matching anyway, which is a superset of
> > > > what switch can do. There's no point in improving a legacy feature
> > > > when it is simultaneously being rendered obsolete.
> > > > 
> > > > > string b = “hello”;
> > > > > auto var = switch(b){
> > > > > case “hi”: { return 42; }
> > > > > case “hello”: { return 43; }
> > > > > default: { return 0; } // probably should be mandatory
> > > > > };
> > > > 
> > > > ```
> > > > b match {
> > > > "hi" => return 42;
> > > > "hello" => return 43;
> > > > _ => return 0;
> > > > }
> > > > ```
> > > > --
> > > > Std-Proposals mailing list
> > > > Std-Proposals_at_[hidden]
> > > > https://lists.isocpp.org/mailman/listinfo.cgi/std-proposals
> > 
> > --
> > Std-Proposals mailing list
> > Std-Proposals_at_[hidden]
> > https://lists.isocpp.org/mailman/listinfo.cgi/std-proposals