[swift-evolution] Revisiting SE-0110

Daryle Walker darylew at mac.com
Sat Jun 24 13:20:00 CDT 2017

> On Jun 24, 2017, at 12:25 PM, Djura Retired Hunter <retired.hunter.djura at gmail.com> wrote:
> I didn't understand your example at all. Care to elaborate?
> Elviro
>> Il giorno 24 giu 2017, alle ore 18:05, Daryle Walker <darylew at mac.com <mailto:darylew at mac.com>> ha scritto:
>>> On Jun 23, 2017, at 7:46 AM, Elviro Rocca via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>>> It's probably late to just casually add a couple of cents to a discussion that has been going for so long, but it seems to me that from a user standpoint, that uses types to structure their programs and define logic and relationships, isomorphic types should be considered the same by the compiler. The added burden of distinguishing between, to say, a function that takes 2 arguments and one that takes a single tuple of two arguments doesn't seem useful at all, at least from the standpoint of the types involves. All the rest, like named parameters or tuple labels, are just really about style and convenience, but isomorphic types, while not strictly equal (the very concept of "equal" is in fact a huge deal in abstract mathematics) are for all means "equivalent" for the world-modeler.
>> Doesn’t seem useful?…
>> let myFunc: (MyTypeAlias) -> Int = /* … */
>> Does the function pointer have a single parameter? Or does it trigger Super-Secret Tuple-Destructing mode and actually indicate two parameters? My secret unknown single type should always be a single type, no matter what kind of type it is.

(A, B, C)  ((A, B), C)  (A, (B, C))

You’re saying partitions aren’t important. I’m saying that they are. Even though the second two tuples above are implemented like the first, I wouldn’t want them to be indistinguishable from an user’s standpoint. I wouldn’t want my two-argument functions magically become a three-argument one due to implementation details.

My previous example will stay an one-argument function for any non-tuple type behind the alias. But if it’s a tuple type, my assumption breaks because your rules would ban tuples from being first-class types.

Daryle Walker
Mac, Internet, and Video Game Junkie
darylew AT mac DOT com 

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