so yeah, walrus operator? ```var next = stack.last...

# language-evolution

[Hullaballoonatic]

so yeah, walrus operator?

var next = stack.last
    get() {
        field = stack.pop()
        field
    }

var next = stack.last
    get() = field := stack.pop()

[karelpeeters]

They special cased when just to be able to avoid adding this operator 🙂

[Hullaballoonatic]

Yeah, I'd like to know why they wanted to avoid it so badly yet added it to when

[Quy D X Nguyen]

What the special case?

[karelpeeters]

when(val x = foo()) is allowed

[karelpeeters]

It's from the last update I think.

[Hullaballoonatic]

Meanwhile you can't do if (val x = foo()) like you can in Java.

[elizarov]

But may I ask “why”? The example code you’ve given is a horrible anti-pattern — a property with a side effect 😱

Of course, there are some legitimate use-cases for “get and assign” operator. They are too infrequent to warrant a special operator, though. In cases where it is really needed you can do this (let’s name it properly in this example to highlight its side effect):

fun moveNext() = stack.pop().also { next = it }

[Hullaballoonatic]

don't iterators have side effects to next also?
and, yeah, i used also in similar code i wrote. I wasn't really writing up this code as a good example of why it'd be nice to have, but instead just showcasing how it works.
i think the better example of where they'd be applicable are in while and if statements:

if ((val n = password.length) < 6) error("pw length of $n is too short. must be >= 6")

[Hullaballoonatic]

in that case, however, using kotlin's standard variable declaration syntax is the clear go-to

[karelpeeters]

Iterator.next() is a function.