switch statements with empty parameters parameters

[Olexandr Rotan]

I would say that the moment there is something except i in switch you are
violating SRP on statement level. If I were to advocate for alike feature,
I would much rather support something like

 var res = switch (i) {
    case < 5 -> 5;
    case > 10 -> 10;
    case null -> 0
    default -> throw new IllegalStateException("Unexpected value: " + new
Object());
};

(something like this is present in .NET). Adding case ... j.length() < 10
-> 20; seems like it steps outside of switch scope, which is pattern
matching on switch argument, to me.

Regrads

On Tue, Oct 1, 2024 at 4:20 PM Brian Goetz <brian.goetz at oracle.com> wrote:

> Yes, this has been considered several times.  It is one of those things
> that seems clever at first, and it is not intrinsically flawed, but over
> time seems less attractive, for a number of reasons.
>
> To start with, let’s recognize that `switch` doesn’t really need to exist;
> it doesn’t express anything that we can’t express with `if` and other
> control flows.  So why do we have it?  Because it is _more constrained_
> than arbitrary if-else-break logic, and therefore we can write simpler
> programs with it.  If we give switch more kinds of jobs to do, we risk
> giving up that simplicity benefit.
>
> The essence of switch is to ask “is this thing one of these, if so, do the
> appropriate thing.”  It started out very limited (limited in selector types
> and the kinds of cases), and we generalized it to more types and more
> powerful cases (through patterns and guards), while at the same time,
> retaining that essence of “pick one based on what this target is.”
>
> So the answer to your question is: yes, it’s been considered; yes, it’s
> not totally dumb (many proposed language features don’t meet this bar); but
> no, it does not seem the best thing we could be working on now.
>
>
> On Oct 1, 2024, at 9:09 AM, mirage <newblood17 at gmail.com> wrote:
>
> Hello.
>
> In the recent years switch has been enhanced and there are some
> discussions about enhancing it even further with try - catch evaluation
> style inside the switch itself.
>
> i was wondering if an additional enhancement could be to be able to use an
> empty parameter switch so we can use switch as a general-purpose
> replacement of if-else chains. Switch has many advantages over if-else
> chains, being these the most relevant.
>
> - The code it's cleaner and more readable, even with nested switch
> expressions.
> - Switch can be an expression, so it can return an assign a value to a
> variable.
>
> nowadays we can use something like this.
>
> var i = someIntMethodParameter;
> var j = someStringMethodParameter
> var res = switch (new Object()){
>     case Object _ when i < 5 -> 5;
>     case Object _ when i > 10 -> 10;
>     case Object _ when j.length() < 10 -> 20;
>     case null -> 0;
>     default -> throw new IllegalStateException("Unexpected value: " + new
> Object());
> };
>
> as we can see here this is effectively a replacement for if-else chains
> that returns the first true case, but there are some problems with this
> syntax and semantics
>
> . I was wondering if it could be a good idea to
>
> *
> };*
>
>
>
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