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

[Brandon Knope]

Are you really surprised that some people don't want this taken away?

The burden should be on those that want it taken out of the language and not those that want it kept. After all something is being removed and it should be a delicate process. 

Don't be surprised when the defenders say it is more readable to them. That is a *sound* argument in my opinion. 

Brandon

Sent from my iPad

> On Jun 13, 2016, at 8:33 AM, Xiaodi Wu via swift-evolution <swift-evolution at swift.org> wrote:
> 
> This is not a sound argument. If your filtering can be expressed as a where clause, then you would only have to read one line into the loop to see it in the form of a guard clause.
> 
> Moreover, if what you're arguing is that you shouldn't ever have to *read* inside the loop to know if a sequence is filtered, how do you propose that we do that? Remove the continue keyword?
> 
>> On Mon, Jun 13, 2016 at 6:16 AM Jean-Daniel Dupas via swift-evolution <swift-evolution at swift.org> wrote:
>> -1 for the removal.
>> 
>> When I read code, I find it far more visible that a loop is over a filter list when the filter clause is on the same line, than when the filter clause is inside the loop.
>> 
>> Having to read the full content of the loop to determine if the list is filtered or not is not an improvement IMHO.
>> 
>> Moreover, I find it far cleaner to use the where clause that having to remember than I have to use the lazy accessor to avoid a performance hit.
>> 
>>>> Le 13 juin 2016 à 06:39, Charlie Monroe via swift-evolution <swift-evolution at swift.org> a écrit :
>>>> 
>>>> 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.
>>>> 
>>>> -- E
>>> 
>>> Not to undermine this fact, but I believe the fact that `where` can be used in a for loop is not widely known. I didn't know about it until about a month ago (haven't really read much docs, but most people don't either).
>>> 
>>> But after I found out about it, I started using it and it IMHO improved readability of my code. Not by much, but it's the little things that make you smile, right?
>>> 
>>> Many people here argument that `where` is a Swift speciality and needs to be learned by the developer - the alternative is to teach the person what's the proper alternative - that using .filter can have performance impact and that the *correct* way is to use guard within the for loop. And that's IMHO much worse than teaching a person about using `where` within a for loop.
>>> 
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