[swift-evolution] [swift-evolution-announce] [Review] SE-0027 Expose code unit initializers on String

Dave Abrahams dabrahams at apple.com
Wed Feb 17 11:59:07 CST 2016

on Tue Feb 16 2016, Kevin Ballard <swift-evolution at swift.org> wrote:

> I'm very much a fan of the end result of this proposal, i.e. some way to
> convert from a collection of code units into a String. Initially I
> thought the proposed API was acceptable, barring some quibbles about
> naming, but I think Dave Abrahams has made some good points in this
> thread, and so I'll just say that I very much support getting this kind
> of functionality in the stdlib, but if Dave Abrahams thinks that the API
> as proposed isn't what we want in the long term, then I'll defer to his
> judgement.

I should be clear: I based that assessment on what the proposal itself
said.  I don't even know the details of the alternative that the
proposal suggests would be better in the long term.  The fact that the
proposal is suggesting we do something that it says might not be the
best long-term solution, with no other justification than that it will
work “in the meantime” leaves me lacking confidence that the proposal
is sufficiently well-considered to accept.

> Also, given the proposed API, the input really should be a SequenceType.
> I recognize that it's calling through to _StringBuffer.fromCodeUnits()
> which takes a CollectionType, but the only reason that takes a
> CollectionType is so it can pre-calculate the size of the UTF-16 buffer,
> and I don't think that limitation should be exposed through the public
> API. It would be better to change _StringBuffer.fromCodeUnits() to take
> a SequenceType and use the _preprocessingPass machinery to choose
> between the fast-path of pre-allocating the buffer and a slow path of
> growing the buffer as needed.
> -Kevin Ballard
> On Thu, Feb 11, 2016, at 04:41 PM, Douglas Gregor wrote:
>> Hello Swift community,
>> The review of SE-0027 "Expose code unit initializers on String"
>> begins now and runs through February 16, 2016. The proposal is
>> available here:
>>> https://github.com/apple/swift-evolution/blob/master/proposals/0027-string-from-code-units.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. When replying, please try to keep the proposal link at
>> the top of the message:
>>> Proposal link:
>>>> https://github.com/apple/swift-evolution/blob/master/proposals/0027-string-from-code-units.md
>>> Reply text
>>>> Other replies
>> 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 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,
>> Doug Gregor
>> Review Manager
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