> On Sep 18, 2017, at 9:47 AM, Adam Kemp <adam_k...@apple.com> wrote:
>
>> Would it be possible to actually fix this? That is, make the code covered by
>> the `await` evaluate synchronous subexpressions first, such that the code
>> sample above is equivalent to this?
>>
>> @IBAction func buttonDidClick(sender:AnyObject) {
>> beginAsync {
>> let $temp1 = self.resizeSwitch.isOn
>> let $temp2 = await downloadImage()
>> let image = await processImage($temp2, resize: $temp1)
>> displayImage(image)
>> }
>> }
>
> That violates the defined order of evaluation for function arguments.
I understand that, but this order of evaluation was designed before we had
`await`. I'm suggesting that, now that we do, we should change the order so
that synchronous subexpressions are evaluated before asynchronous ones.
> You could also write code in which the (async) first argument function call
> has side effects that alter the result of the second argument expression. I’m
> not saying that’s good code, but it’s possible, and the language defines the
> order of evaluation so that code like that will have a predictable behavior.
You could write something like that, but as you say, that's not necessarily
good code. Honestly, I don't think you can write good code that depends on one
part of an expression being evaluated after an async call in another part of
the expression completes.
--
Brent Royal-Gordon
Architechies
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