[swift-evolution] Proposal: An assignment operator := that ensures nil before assignment.

[Amir Michail]

> On Feb 27, 2016, at 11:30 AM, Stephen Celis <stephen.celis at gmail.com> wrote:
> 
>> On Feb 27, 2016, at 11:28 AM, Amir Michail via swift-evolution <swift-evolution at swift.org> wrote:
>> 
>> It’s a convenience feature that saves lots of finger typing.
>> 
>> Which would you rather have:
>> 
>> precondition( x == nil )
>> x = 3
>> 
>> OR
>> 
>> x: = 3
>> 
>> ?
> 
> A bunch of us have tried to point out that toy examples like these are not helpful enough.
> 

Here’s a use case. Suppose you are filling out a dictionary in some non-trivial way. However, it should be the case that the value for each key is computed and assigned only once. And so you would use the := operator to ensure this: dictionary[k] := value

> You're not addressing the actual content and questions of any of your replies, Amir. Would you please take the time and effort to do so?
> 
> --
> Stephen