[swift-evolution] [Pitch] Retiring `where` from for-in loops

Xiaodi Wu xiaodi.wu at gmail.com
Fri Jun 10 14:09:11 CDT 2016

On Fri, Jun 10, 2016 at 2:06 PM, Goffredo Marocchi <panajev at gmail.com>

> I was not advocating the lack of constraints, programmers like all other
> artists (and engineers, which are artists too ;)), but that the beauty is
> the moderation of the two extremes :). ... and that architects leave the
> problems you are talking about to the structural engineer :P.
> Gravity is a constrain, but a different one than having to use only a
> certain pencil to do your sketches with and only being able to use Windows
> 95 OSR 3 to work on or even weirder limitations.

The question is, does removing `where` feel to you like going from OS X
10.11 to Windows 95, or is it more like going from OS X 10.11.4 to OS X

> On Fri, Jun 10, 2016 at 7:59 PM, Xiaodi Wu <xiaodi.wu at gmail.com> wrote:
>> On Fri, Jun 10, 2016 at 1:11 PM, Goffredo Marocchi <panajev at gmail.com>
>> wrote:
>>> I think sometimes the community in this mailing list loses sight on the
>>> fact that coding is a creative  endeavour much similar to architectural
>>> design or painting. There may be math and well researched and structured
>>> ideas in place, but it requires creativity too.
>> Architects are constrained to craft buildings that will stand in the face
>> of gravity, and even painters don't have pigments for every color visible
>> to the human eye. There's a wonderful novel, _Gadsby_, written without the
>> letter 'e'; I haven't read it but I understand it's truly an
>> accomplishment. This is not so drastic here. In this case, the apt analogy
>> would be that we find the letter 'a with circle on top' to be posing some
>> pesky problems; do you think you could write a novel in English without
>> using 'a with circle on top'? I wager that your creativity will not suffer
>> (unless your novel describes a trip to IKEA, in which case I'm sorry).
>>> Trying to force a strict one size fits all The One True standard usually
>>> ends up fragmenting the standard further, by adding yet another take on
>>> what is the most orthodox implementation and who are the heretics...
>>> I do not think dismissing the idea of having more than one way of
>>> skinning the proverbial cat as an anti-goal is doing a good service to the
>>> community or the language as it completely disregards context, people
>>> differing idea of the subjective best coding style and patterns (which
>>> pattern do I use? Which algorithm do I use to sort this data set with? A
>>> good engineer will give you a direct and concise answer, but a better one
>>> will say "it depends... What's the context? What is the problem I need to
>>> solve, what are the constraints and the data set I am working on?").
>>> The way some users seem to want Swift to follow sounds like protecting
>>> users from mistakes by sometimes removing the ability which could lead to
>>> mistakes in the first place, but that removes all the good things you could
>>> do if you were to trust developers with the extra responsibility.
>>> Sent from my iPhone
>>> On 10 Jun 2016, at 18:30, let var go via swift-evolution <
>>> swift-evolution at swift.org> wrote:
>>> I respect that anti-goal, but I think being over-rigid about limiting
>>> developers' choice of expression is also an anti-goal.
>>> To me, it is like guard statements vs. if-let statements. Some people
>>> find one to be more clear than the other. Often times the best choice
>>> depends on the context. Sometimes a guard statement can be re-written as an
>>> if-let statement in a way that makes the code more clear, and vice versa.
>>> And different people will inevitably have different personal preferences -
>>> their own "style", if you will - and will favor one over the other. But it
>>> would be a mistake to force everyone into one box in order to prevent the
>>> fracturing of the Swift community into "dialects."
>>> But most importantly (and this is really the kicker for me) there are
>>> times when the "where" syntax provides the maximum amount of clarity in the
>>> context of my code, and I don't want to lose that expressive power.
>>> On Fri, Jun 10, 2016 at 10:17 AM Xiaodi Wu <xiaodi.wu at gmail.com> wrote:
>>>> I think this idea--if you don't like it, then you don't have to use
>>>> it--is indicative of a key worry here: it's inessential to the language and
>>>> promotes dialects wherein certain people use it and others wherein they
>>>> don't. This is an anti-goal.
>>>> On Fri, Jun 10, 2016 at 12:10 let var go <letvargo at gmail.com> wrote:
>>>>> Leave it in!
>>>>> It's a great little tool. I don't use it very often, but when I do it
>>>>> is because I've decided that in the context of that piece of code it does
>>>>> exactly what I want it to do with the maximum amount of clarity.
>>>>> If you don't like it, then don't use it, but I can't see how it
>>>>> detracts from the language at all.
>>>>> The *only* argument that I have heard for removing it is that some
>>>>> people don't immediately intuit how to use it. I didn't have any trouble
>>>>> with it at all. It follows one of the most basic programming patterns ever:
>>>>> "For all x in X, if predicate P is true, do something." The use of the
>>>>> keyword "where" makes perfect sense in that context, and when I read it out
>>>>> loud, it sounds natural: "For all x in X where P, do something." That is an
>>>>> elegant, succinct, and clear way of stating exactly what I want my program
>>>>> to do.
>>>>> I don't doubt that it has caused some confusion for some people, but
>>>>> I'm not sold that that is a good enough reason to get rid of it. It seems
>>>>> strange to get rid of a tool because not everyone understands how to use it
>>>>> immediately, without ever having to ask a single question. As long as its
>>>>> not a dangerous tool (and it isn't), then keep it in the workshop for those
>>>>> times when it comes in handy. And even if there is some initial confusion,
>>>>> it doesn't sound like it lasted that long. It's more like, "Does this work
>>>>> like X, or does this work like Y? Let's see...oh, it works like X. Ok."
>>>>> That's the entire learning curve...about 5 seconds of curiosity followed by
>>>>> the blissful feeling of resolution.
>>>>> On Fri, Jun 10, 2016 at 9:32 AM Xiaodi Wu via swift-evolution <
>>>>> swift-evolution at swift.org> wrote:
>>>>>> On Fri, Jun 10, 2016 at 11:23 AM, Sean Heber via swift-evolution <
>>>>>> swift-evolution at swift.org> wrote:
>>>>>>> > And to follow-up to myself once again, I went to my "Cool 3rd
>>>>>>> Party Swift Repos" folder and did the same search. Among the 15 repos in
>>>>>>> that folder, a joint search returned about 650 hits on for-in (again with
>>>>>>> some false positives) and not a single for-in-while use.
>>>>>>> Weird. My own Swift projects (not on Github :P) use “where” all the
>>>>>>> time with for loops. I really like it and think it reads *and* writes far
>>>>>>> better as well as makes for nicer one-liners. In one project, by rough
>>>>>>> count, I have about 20 that use “where” vs. 40 in that same project not
>>>>>>> using “where”.
>>>>>>> In another smaller test project, there are only 10 for loops, but
>>>>>>> even so one still managed to use where.
>>>>>>> Not a lot of data without looking at even more projects, I admit,
>>>>>>> but this seems to suggest that the usage of “where” is going to be very
>>>>>>> developer-dependent. Perhaps there’s some factor of prior background at
>>>>>>> work here? (I’ve done a lot of SQL in another life, for example.)
>>>>>> That is worrying if true, because it suggests that it's enabling
>>>>>> 'dialects' of Swift, an explicit anti-goal of the language.
>>>>>>> I feel like “where” is a more declarative construct and that we
>>>>>>> should be encouraging that way of thinking in general. When using it, it
>>>>>>> feels like “magic” for some reason - even though there’s nothing special
>>>>>>> about it. It feels like I’ve made the language work *for me* a little bit
>>>>>>> rather than me having to contort my solution to the will of the language.
>>>>>>> This may be highly subjective.
>>>>>>> l8r
>>>>>>> Sean
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