> On Jan 18, 2017, at 8:57 AM, Matthew Johnson <matt...@anandabits.com> wrote:
>
>
>> On Jan 18, 2017, at 10:54 AM, Joe Groff via swift-evolution
>> <swift-evolution@swift.org> wrote:
>>
>>
>>> On Jan 18, 2017, at 8:50 AM, Tony Allevato <tony.allev...@gmail.com> wrote:
>>>
>>> Good point—I hadn't considered the distinction.
>>>
>>> Does that mean a future version of Swift might allow `let` in a protocol to
>>> indicate a value that must be immutable after initialization, such that a
>>> computed `var { get }` wouldn't satisfy it?
>>
>> It's conceivable that even computed `let` properties could be supported, if
>> the getter implementation is a pure function of `self`.
>
> How would that work when `self` is mutable?
The exact meaning of "pure" and "immutable" would have to be designed. To a
first approximation, you could say a pure method would only be able to read
immutable global or class data (which is itself `let` or `pure func`, not
anything that's potentially mutable) in addition to its own arguments.
-Joe
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