<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div><blockquote type="cite" class=""><div class="">On Jan 25, 2017, at 12:47 PM, Jacob Bandes-Storch via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:</div><div class="">Really? My observation from a quick test is that "a? = b" assigns b to a if a already has a value, or does nothing if it's nil. This is sort of the opposite of what's being proposed, which is that "a ?= b" should assign to a only if it does NOT have a value.<br class=""></div></blockquote><div><br class=""></div>Right. On the other hand, this does seem like a poor spelling for the operator, given the ease of confusion.</div><div><br class=""></div><div>Also, I'm finding it hard to imagine a use for this where the equivalent ?? invocation wouldn't be *much* clearer. It just feels like you must be doing something backwards — "I've filled in a default value for this variable, now overwrite it if this other value exists". Wouldn't the reverse generally be better?</div><div><br class=""></div><div>John.</div><div><br class=""><blockquote type="cite" class=""><div class=""><div class="gmail_quote"><div dir="ltr" class="">On Wed, Jan 25, 2017 at 9:33 AM Joe Groff via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:<br class=""></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><br class="gmail_msg">
> On Jan 25, 2017, at 8:40 AM, Nichi Shin via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="gmail_msg" target="_blank">swift-evolution@swift.org</a>> wrote:<br class="gmail_msg">
><br class="gmail_msg">
> I’d like to propose a new operator for optional assignment in Swift.<br class="gmail_msg">
><br class="gmail_msg">
> The idea is that by using this operator (e.g. by doing a ?= b), the optional on the right would be assigned to the variable on the left only when it has something to assign (i.e. when it's not nil).<br class="gmail_msg">
<br class="gmail_msg">
`a? = b` already does this. Maybe we need a fixit to make that more apparent, though.<br class="gmail_msg">
<br class="gmail_msg">
-Joe<br class="gmail_msg">
<br class="gmail_msg">
><br class="gmail_msg">
> The implementation could be something as follows:<br class="gmail_msg">
><br class="gmail_msg">
> /// Optional Assignment Operator<br class="gmail_msg">
> infix operator ?=: AssignmentPrecedence<br class="gmail_msg">
><br class="gmail_msg">
> func ?=<T>(left: inout T, right: T?) {<br class="gmail_msg">
> if right != nil {<br class="gmail_msg">
> left = right!<br class="gmail_msg">
> }<br class="gmail_msg">
> }<br class="gmail_msg">
><br class="gmail_msg">
> func ?=<T>(left: inout T?, right: T?) {<br class="gmail_msg">
> if right != nil {<br class="gmail_msg">
> left = right<br class="gmail_msg">
> }<br class="gmail_msg">
> }<br class="gmail_msg">
><br class="gmail_msg">
> I hope you will consider adding this on a future release of this great programming language.<br class="gmail_msg">
><br class="gmail_msg">
> Kind regards,<br class="gmail_msg">
> N. S.<br class="gmail_msg">
> _______________________________________________<br class="gmail_msg">
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