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

[David Waite]

I’m a bit late to this conversation, and I don’t totally understand the goal.

There are a *lot* of things you can do in for…in loop with pattern matching that also would supposedly go against this interpretation of approachability. Pattern matching in general might be considered to go against this interpretation.

Is this pitch saying statements such as:

	for i in 1..<100 where i%2 == 1 {…} 

should be disallowed, while statements like

	for case let view? in views { … }

are still approachable enough to warrant being supported in the language?

FWIW, I wouldn’t support removing where based on current arguments without either the keyword “where" being eliminated completely from the language, and/or adding equivalent intuitive functionality to Sequence with same-class performance, e.g. a .where(...) equivalent to .lazy.filter(…). 

I’ve known about and used the feature since it was first added to Swift (learned via the language book), and don’t fully understand the confusion that some developers may have - especially since ‘while’ is already a keyword and could have been used if that was the actual semantics.

-DW

> On Jun 14, 2016, at 10:32 AM, Xiaodi Wu via swift-evolution <swift-evolution at swift.org> wrote:
> 
> And from the WWDC Platforms SOTU: "Swift is super simple and approachable.... It's great as a first language. And in fact, we think this is so important that when we designed Swift this was an explicit design goal."
> 
> I would be absolutely against adding any more sugar to the for loop. In that sense, `where` sets a terrible example that certain features of sequences deserve contextual sugar. (And before someone points it out again, I've already argued why `for...in` holds its own weight, namely difficulty of writing a correct `while` replacement and progressive disclosure to the learner so that the concept of iterators can be learned afterwards.)
> 
> In short, I would very much be opposed to adding keywords "for fun."

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