[swift-evolution] [Review] SE-0065 A New Model for Collections and Indices

[Gwendal Roué]

Hello,

I have a user question regarding the proposed range types that replace the old range/interval.

The old hierachy allowed me to turn ranges to SQL expressions through the following mapping (see https://github.com/groue/GRDB.swift/blob/v0.57.0/GRDB/FetchRequest/SQLOperator.swift#L335-L365)

	1. Range<BidirectionalIndexType>
	expr BETWEEN self.startIndex AND self.endIndex.predecessor()

	2. ClosedInterval
	expr BETWEEN self.start AND self.end

	3. HalfOpenInterval
	expr >= start AND x < end

This would let me generate SQL for 0..<18 and "A"..<"B", as below:

	// SELECT * FROM "persons" WHERE ("age" BETWEEN 0 AND 17)
	Person.filter((0..<18).contains(Col.age))

	// SELECT * FROM "persons" WHERE ("age" BETWEEN 0 AND 17)
	Person.filter((0...17).contains(Col.age))

	// SELECT * FROM "persons" WHERE ("name" BETWEEN 'A' AND 'z')
	Person.filter(("A"..."z").contains(Col.name))

	// SELECT * FROM "persons" WHERE (("name" >= 'A') AND ("name" < 'z'))
	Person.filter(("A"..<"z").contains(Col.name))

Will it still be possible with the new protocol and types? Especially, how to I generate "BETWEEN 0 AND 17" from 0..<18 without a supporting collection that gives me the predecessor of 18?

Gwendal Roué

> Le 10 avr. 2016 à 23:41, Chris Lattner via swift-evolution <swift-evolution at swift.org> a écrit :
> 
> Hello Swift community,
> 
> The review of "A New Model for Collections and Indices" begins now and runs through April 18th. The proposal is available here:
> 
> 	https://github.com/apple/swift-evolution/blob/master/proposals/0065-collections-move-indices.md
> 
> Reviews are an important part of the Swift evolution process. All reviews should be sent to the swift-evolution mailing list at:
> 	https://lists.swift.org/mailman/listinfo/swift-evolution
> or, if you would like to keep your feedback private, directly to the review manager.
> 
> 
> What goes into a review?
> 
> The goal of the review process is to improve the proposal under review through constructive criticism and, eventually, determine the direction of Swift. When writing your review, here are some questions you might want to answer in your review:
> 
> 	* What is your evaluation of the proposal?
> 	* Is the problem being addressed significant enough to warrant a change to Swift?
> 	* Does this proposal fit well with the feel and direction of Swift?
> 	* If you have you used other languages or libraries with a similar feature, how do you feel that this proposal compares to those?
> 	* How much effort did you put into your review? A glance, a quick reading, or an in-depth study?
> 
> More information about the Swift evolution process is available at
> 
> 	https://github.com/apple/swift-evolution/blob/master/process.md
> 
> Thank you,
> 
> -Chris Lattner
> Review Manager
> 
> 
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