# [swift-evolution] [swift-evolution-announce] [Review] SE-0024 "Optional Value Setter `??=`"

davesweeris at mac.com davesweeris at mac.com
Tue Feb 16 13:35:00 CST 2016

```Oops, I meant “if x is not nil”. Everywhere else, the ? or ?? "goes through” when the value in question is not nil. In this case, something happens when the value *is* nil.

> On Feb 16, 2016, at 8:13 AM, Ross O'Brien <narrativium+swift at gmail.com> wrote:
>
> "y is assigned to x if x is nil" is exactly what "x ??= y" means. If x is nil, x is assigned the value of y; if x is not nil, it doesn't matter what y is.
>
> This is exactly consistent with the boolean operator ||= ; "x ||= y" means "y is assigned to x if x is false" - if x is false, x is assigned the value of y; if x is true, it doesn't matter what y is.)
>
> Why do you think it means the opposite?
>
> On Tue, Feb 16, 2016 at 1:24 PM, David Sweeris via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
> -1, because in my mind, "x ??= y" kinda looks like "y is assigned to x iff y isn't nil", or, if you associate the ?? part with the lhs, "y is assigned to x if x is nil", neither of which is what the proposed operator means. In fact, the 2nd case is the *opposite* of what ??= means in this proposal.
>
> To be clear, it's the syntax that I'm opposed to, not the concept.
>
> - Dave Sweeris
>
> On Feb 12, 2016, at 23:15, Douglas Gregor <dgregor at apple.com <mailto:dgregor at apple.com>> wrote:
>
>> Hello Swift community,
>>
>> The review of SE-0024 "Optional Value Setter `??=`" begins now and runs through February 18, 2016. The proposal is available here:
>>
>> https://github.com/apple/swift-evolution/blob/master/proposals/0024-optional-value-setter.md <https://github.com/apple/swift-evolution/blob/master/proposals/0024-optional-value-setter.md>
>> Reviews are an important part of the Swift evolution process. All reviews should be sent to the swift-evolution mailing list at
>>
>> https://lists.swift.org/mailman/listinfo/swift-evolution <https://lists.swift.org/mailman/listinfo/swift-evolution>
>> or, if you would like to keep your feedback private, directly to the review manager. When replying, please try to keep the proposal link at the top of the message:
>>
>>
>> https://github.com/apple/swift-evolution/blob/master/proposals/0024-optional-value-setter.md <https://github.com/apple/swift-evolution/blob/master/proposals/0024-optional-value-setter.md>
>>
>> Other replies
>>  <https://github.com/apple/swift-evolution#what-goes-into-a-review-1>What goes into a review?
>>
>> The goal of the review process is to improve the proposal under review through constructive criticism and, eventually, determine the direction of Swift. When writing your review, here are some questions you might want to answer in your review:
>>
>> What is your evaluation of the proposal?
>> Is the problem being addressed significant enough to warrant a change to Swift?
>> Does this proposal fit well with the feel and direction of Swift?
>> If you have used other languages or libraries with a similar feature, how do you feel that this proposal compares to those?
>> How much effort did you put into your review? A glance, a quick reading, or an in-depth study?
>>
>> https://github.com/apple/swift-evolution/blob/master/process.md <https://github.com/apple/swift-evolution/blob/master/process.md>
>> Thank you,
>>
>> Doug Gregor
>>
>> Review Manager
>>
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