[swift-dev] Make offset index available for String

[Kelvin Ma]

perhaps i’m biased because most of the work i do is on strings that are
meant to be machine read and written but if you ask me, user-facing unicode
strings are the special case and it seems the entire API is optimized for
them, and not more common ASCII strings.

On Thu, Dec 14, 2017 at 3:40 PM, Wallacy <wallacyf at gmail.com> wrote:

> 95% ASCII? Even if you forgot the rest of the World and consider only US
> this doesn’t seems right.
>
> But of course people (in the general) don’t care about Unicode Clusters.
> Because that, we should focus on keep Unicode string manipulation easy,
> instead just forget the Unicode rules.
>
>
> Em qui, 14 de dez de 2017 às 17:28, Kelvin Ma via swift-dev <
> swift-dev at swift.org> escreveu:
>
>> I think there’s a middle ground here as the current API is overly complex
>> and general. 95% of the time people are dealing with ASCII strings and
>> don’t care about things like unicode cluster boundaries and whatnot
>>
>> On Thu, Dec 14, 2017 at 12:13 PM, Jordan Rose via swift-dev <
>> swift-dev at swift.org> wrote:
>>
>>> We really don't want to make subscripting a non-O(1) operation. That
>>> just provides false convenience and encourages people to do the wrong thing
>>> with Strings anyway.
>>>
>>> I'm always interested in why people want this kind of ability. Yes, it's
>>> nice for teaching programming to be able to split strings on character
>>> boundaries indexed by integers, but where does it come up in real life? The
>>> most common cases I see are trying to strip off the first or last
>>> character, or a known prefix or suffix, and I feel like we should have
>>> better answers for those than "use integer indexes" anyway.
>>>
>>> Jordan
>>>
>>>
>>> On Dec 13, 2017, at 22:30, Cao, Jiannan via swift-dev <
>>> swift-dev at swift.org> wrote:
>>>
>>> Hi,
>>>
>>> I would like to discuss the String.Index problem within Swift. I know
>>> the current situation of String.Index is based on the nature of the
>>> underlaying data structure of the string.
>>>
>>> But could we just make String.Index contain offset information? Or make
>>> offset index subscript available for accessing character in String?
>>>
>>> for example:
>>>
>>> let a = "01234"
>>> print(a[0]) // 0
>>> print(a[0...4]) // 01234
>>> print(a[...]) // 01234
>>> print(a[..<2]) // 01
>>> print(a[...2]) // 012
>>> print(a[2...]) // 234
>>> print(a[2...3]) // 23
>>> print(a[2...2]) // 2
>>> if let number = a.index(of: "1") {
>>>     print(number) // 1
>>>     print(a[number...]) // 1234
>>> }
>>>
>>>
>>>
>>> 0 equals to Collection.Index of collection.index(startIndex, offsetBy: 0)
>>> 1 equals to Collection.Index of collection.index(startIndex, offsetBy:
>>> 1)
>>> ...
>>> we keep the String.Index, but allow another kind of index, which is
>>> called "offsetIndex" to access the String.Index and the character in the
>>> string.
>>> Any Collection could use the offset index to access their element,
>>> regarding the real index of it.
>>>
>>> I have make the Collection OffsetIndexable protocol available here, and
>>> make it more accessible for StringProtocol considering all API related to
>>> the index.
>>>
>>> https://github.com/frogcjn/OffsetIndexableCollection-
>>> String-Int-Indexable-
>>>
>>> If someone want to make the offset index/range available for any
>>> collection, you just need to extend the collection:
>>>
>>> extension String : OffsetIndexableCollection {
>>> }
>>> extension Substring : OffsetIndexableCollection {
>>> }
>>>
>>>
>>>
>>> I hope the Swift core team could consider bring the offset index to
>>> string, or make it available to other collection, thus let developer to
>>> decide whether their collection could use offset indices as an assistant
>>> for the real index of the collection.
>>>
>>>
>>> Thanks!
>>> Jiannan
>>>
>>>
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>>>
>>>
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