[swift-evolution] [Proposal] More lenient subscript methods over Collections

[Luis Henrique B. Sousa]

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> 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>> 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>> 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
>>>
>>>
>>> _______________________________________________
>>> swift-evolution mailing list
>>> swift-evolution at swift.org <mailto:swift-evolution at swift.org>
>>> https://lists.swift.org/mailman/listinfo/swift-evolution
>>>
>>
>>
>>
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