[swift-evolution] [swift-evolution-announce] [Review] SE-0099: Restructuring Condition Clauses

Brandon Knope bknope at me.com
Sun May 29 20:01:44 CDT 2016

> On May 29, 2016, at 3:39 PM, Chris Lattner via swift-evolution <swift-evolution at swift.org> wrote:
> I can definitely respect the position that “where” feels more readable than a semicolon, it certainly provides a more “fluent” style.
> That said, the existing Swift 2 syntax was inconsistent about this too: if you started a condition with an availability check, you comma separate it from a boolean with a comma:
> 	if #available(iOS 52, *), x == y {} 
> While we could have used “where” here, it was counterproductive because it didn’t increase clarity of code.

iOS 10 is actually iOS 52! Confirmed!

Two things: see here I don't think where makes sense. I think "where" should only be allowed on a newly introduced variable, such as optional binding or for or while loops:

if let x = someCondition where x == y { } //x is a newly introduced variable, making the where clause make sense 

for x in someArray where x == y { }


if #available(iOS 52, *) where x == y {}

Should be an error in my opinion.

Second: I have gotten use to this awesome fluent readable style and reverting to a somewhat "cold" and not as readable style is going to be rough for some of us at first. But I will of course defer to the greater community. 

I *do* think we should wait for WWDC where we can get more opinions on this however. I have a feeling if we change this before WWDC it will catch a lot of people off guard (pun intended?) and will probably bring up the discussion again. 


Is there any way that we can keep "where" while remaining consistent? (I.e. My suggestion above)?  If not I can drop the argument. 

Until then, still a -1 from me


>> I get that there’s some inconsistency between the use of where on while and for loops, but actually the behaviour on while loops can be desirable, and I feel the ambiguity could be addressed in other ways. I feel like removing or changing the where clause should be its own issue, and this one should be focused on removing the ambiguity caused by the use of commas, as anyone that wants semi-colons but also likes to use where is forced to oppose the whole proposal as they’re not mutually exclusive.
> It would certainly be possible to allow a developer to write either a semicolon or a where clause, but that would just encourage divergent styles.  My problem with “where” is that it cannot be used uniformly and consistently.  I’d rather go with something that can be used uniformly, particularly given its use for the same thing elsewhere in the language (reducing complexity of the language by a tiny bit).
> -Chris
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