[swift-evolution] [Proposal] More lenient subscript methods over Collections
Luis Henrique B. Sousa
lshsousa at gmail.com
Mon May 16 02:45:58 CDT 2016
Yes. The suggested implementation does use min/max:
https://github.com/luish/swift-evolution/blob/more-lenient-subscripts/proposals/nnnn-more-lenient-collections-subscripts.md#detailed-design
- Luis
On Sun, May 15, 2016 at 3:42 PM, Maximilian Hünenberger <
m.huenenberger at me.com> wrote:
> I brought these up because the current implementation produces an error in
> these cases. You have to insert additional min/max operations.
>
> Am 15.05.2016 um 16:38 schrieb Luis Henrique B. Sousa <lshsousa at gmail.com
> >:
>
> Exactly, the idea is to return an empty array just like other languages
> do. (e.g. python)
>
> - Luis
>
> On Sun, May 15, 2016 at 10:13 AM, Vladimir.S via swift-evolution <
> swift-evolution at swift.org> wrote:
>
>> On 15.05.2016 0:09, Maximilian Hünenberger via swift-evolution wrote:
>>
>>> One point which should be discussed is the following behaviour:
>>>
>>> let array = [0]
>>> // ranges are completely out of bounds and produce an error
>>> array[clamping: 1...2] // error
>>> array[clamping: -2...-1] // error
>>>
>>> Should a range which has no intersection with the indices of the
>>> collection
>>> produce an error or just clamp to 0..<0 respectively endIndex..<endIndex?
>>>
>>
>> I expect it will returns [] i.e. empty array, as no elements with
>> 1...2(-2..-1) indexes in the array. I understand `clamping` similar as
>> 'bounded','in these bounds'. And as soon as [0,1,2,3,4][clamping:2...10]
>> will silently move the right position to allowed index(4), and
>> [0,1,2,3,4][clamping:-2...0] will move left position to 0, I expect that
>> in [0][clamping: 1...2] will try to move both limits to allowed, and as no
>> intersection - silently return empty array.
>>
>>
>>> Best regards
>>> Maximilian
>>>
>>> Am 13.05.2016 um 17:10 schrieb Luis Henrique B. Sousa via swift-evolution
>>> <swift-evolution at swift.org <mailto:swift-evolution at swift.org>>:
>>>
>>> It seems that there is a consensus that this proposal might be a good
>>>> addition to the standard library. All comments on this thread in the
>>>> past
>>>> few weeks were related to naming, not around the behaviour or validity
>>>> of
>>>> the proposed methods. So I will submit this proposal for review very
>>>> soon
>>>> assuming that nobody else has strong arguments against it. :-)
>>>>
>>>> Proposal:
>>>> https://github.com/luish/swift-evolution/blob/more-lenient-subscripts/proposals/nnnn-more-lenient-collections-subscripts.md
>>>>
>>>> If you have any corrections or suggestions to the proposal text itself,
>>>> please comment on this gist:
>>>> https://gist.github.com/luish/832c34ee913159f130d97a914810dbd8
>>>> (or pull request to my repo)
>>>>
>>>> Regards,
>>>>
>>>> - Luis
>>>>
>>>> On Tue, May 10, 2016 at 4:13 PM, Luis Henrique B. Sousa
>>>> <lshsousa at gmail.com <mailto:lshsousa at gmail.com>> wrote:
>>>>
>>>> Please let me know if you have more suggestions or corrections on
>>>> this proposal.
>>>> I'm tempted to submit it for review. :-)
>>>>
>>>> - Luis
>>>>
>>>> On Tue, May 10, 2016 at 8:53 AM, Luis Henrique B. Sousa
>>>> <lshsousa at gmail.com <mailto:lshsousa at gmail.com>> wrote:
>>>>
>>>> It sounds good, thanks for you suggestions @Vladimir, @Patrick
>>>> and @Brent.
>>>>
>>>> I've just updated the proposal:
>>>>
>>>> https://github.com/luish/swift-evolution/blob/more-lenient-subscripts/proposals/nnnn-more-lenient-collections-subscripts.md#detailed-design
>>>>
>>>> - Luis
>>>>
>>>> On Tue, May 10, 2016 at 6:50 AM, Vladimir.S via swift-evolution
>>>> <swift-evolution at swift.org <mailto:swift-evolution at swift.org>>
>>>> wrote:
>>>>
>>>> Yes, I feel like 'within' is much better than 'bounded'.
>>>>
>>>> How about such changes in proposal:
>>>>
>>>> a[bounded: -1 ..< 5] --> a[within: -1 ..< 5] (or
>>>> a[inside:
>>>> -1 ..< 5] )
>>>>
>>>> a[optional: 0 ..< 5] --> a[checking: 0 ..< 5]
>>>> a[optional: 5] --> a[checking: 5]
>>>>
>>>> ?
>>>>
>>>> On 10.05.2016 6:27, Patrick Smith via swift-evolution wrote:
>>>>
>>>> I like the idea of the of the bounded subscript, however
>>>> the optional one I
>>>> feel could be used for clumsy code.
>>>>
>>>> .first and .last have value, but once you start stepping
>>>> several arbitrary
>>>> indices in, then that code is likely fragile?
>>>>
>>>>
>>>> I can think of ‘within’, ‘inside’ and ‘intersecting’ as
>>>> alternative names
>>>> for ‘bounded’ that attempt to explain what is going on:
>>>>
>>>> let a = [1, 2, 3]
>>>>
>>>> a[within: 0 ..< 5] // [1, 2, 3]
>>>> a[inside: 0 ..< 5] // [1, 2, 3]
>>>> a[intersecting: 0 ..< 5] // [1, 2, 3]
>>>>
>>>>
>>>> On 28 Apr 2016, at 10:11 PM, Luis Henrique B. Sousa
>>>> via swift-evolution
>>>> <swift-evolution at swift.org
>>>> <mailto:swift-evolution at swift.org>
>>>> <mailto:swift-evolution at swift.org
>>>> <mailto:swift-evolution at swift.org>>> wrote:
>>>>
>>>> As we have discussed throughout this thread, the
>>>> initial proposal was
>>>> modified to include alternative subscript methods
>>>> instead of modifying
>>>> the default operator/subscript behaviour.
>>>> The first draft is
>>>> here:
>>>>
>>>> https://github.com/luish/swift-evolution/blob/more-lenient-subscripts/proposals/nnnn-more-lenient-collections-subscripts.md
>>>>
>>>> I've also put this as a gist so that you can leave
>>>> comments with respect
>>>> to the proposal document itself. Any suggestion or
>>>> help is very welcome.
>>>>
>>>> https://gist.github.com/luish/832c34ee913159f130d97a914810dbd8
>>>>
>>>> Regards,
>>>>
>>>> - Luis
>>>>
>>>> On Mon, Apr 11, 2016 at 1:23 PM, Luis Henrique B.
>>>> Sousa
>>>> <lshsousa at gmail.com <mailto:lshsousa at gmail.com>
>>>> <mailto:lshsousa at gmail.com
>>>>
>>>> <mailto:lshsousa at gmail.com>>> wrote:
>>>>
>>>> This proposal seeks to provide a safer ..< (aka
>>>> half-open range
>>>> operator) in order to avoid **Array index out of
>>>> range** errors in
>>>> execution time.
>>>>
>>>> Here is my first draft for this proposal:
>>>>
>>>>
>>>> https://github.com/luish/swift-evolution/blob/half-open-range-operator/proposals/nnnn-safer-half-open-range-operator.md
>>>>
>>>> In short, doing that in Swift causes a runtime
>>>> error:
>>>>
>>>> leta =[1,2,3]
>>>> letb =a[0..<5]
>>>> print(b)
>>>>
>>>> > Error running code:
>>>> > fatal error: Array index out of range
>>>>
>>>> The proposed solution is to slice the array
>>>> returning all elements
>>>> that are below the half-open operator, even
>>>> though the number of
>>>> elements is lesser than the ending of the
>>>> half-open operator. So the
>>>> example above would return [1,2,3].
>>>> We can see this very behaviour in other
>>>> languages, such as Python and
>>>> Ruby as shown in the proposal draft.
>>>>
>>>> This would eliminate the need for verifications
>>>> on the array size
>>>> before slicing it -- and consequently runtime
>>>> errors in cases when
>>>> the programmer didn't.
>>>>
>>>> Viewing that it is my very first proposal, any
>>>> feedback will be helpful.
>>>>
>>>> Thanks!
>>>>
>>>> Luis Henrique Borges
>>>> @luishborges
>>>>
>>>>
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