> On Jan 25, 2017, at 12:47 PM, Jacob Bandes-Storch via swift-evolution > <swift-evolution@swift.org> wrote: > 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.
Right. On the other hand, this does seem like a poor spelling for the operator, given the ease of confusion. 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? John. > On Wed, Jan 25, 2017 at 9:33 AM Joe Groff via swift-evolution > <swift-evolution@swift.org <mailto:swift-evolution@swift.org>> wrote: > > > On Jan 25, 2017, at 8:40 AM, Nichi Shin via swift-evolution > > <swift-evolution@swift.org <mailto:swift-evolution@swift.org>> wrote: > > > > I’d like to propose a new operator for optional assignment in Swift. > > > > 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). > > `a? = b` already does this. Maybe we need a fixit to make that more apparent, > though. > > -Joe > > > > > The implementation could be something as follows: > > > > /// Optional Assignment Operator > > infix operator ?=: AssignmentPrecedence > > > > func ?=<T>(left: inout T, right: T?) { > > if right != nil { > > left = right! > > } > > } > > > > func ?=<T>(left: inout T?, right: T?) { > > if right != nil { > > left = right > > } > > } > > > > I hope you will consider adding this on a future release of this great > > programming language. > > > > Kind regards, > > N. S. > > _______________________________________________ > > swift-evolution mailing list > > swift-evolution@swift.org <mailto:swift-evolution@swift.org> > > https://lists.swift.org/mailman/listinfo/swift-evolution > > <https://lists.swift.org/mailman/listinfo/swift-evolution> > > _______________________________________________ > swift-evolution mailing list > swift-evolution@swift.org <mailto:swift-evolution@swift.org> > https://lists.swift.org/mailman/listinfo/swift-evolution > <https://lists.swift.org/mailman/listinfo/swift-evolution> > _______________________________________________ > swift-evolution mailing list > swift-evolution@swift.org > https://lists.swift.org/mailman/listinfo/swift-evolution
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