# [swift-evolution] [Draft]: Introducing a striding(by:) method on 3.0 ranges

Xiaodi Wu xiaodi.wu at gmail.com
Sat Apr 9 03:27:22 CDT 2016

On Sat, Apr 9, 2016 at 5:44 AM, Wallacy via swift-evolution
<swift-evolution at swift.org> wrote:
> Just as note, i think the sintax should be:
>
> 0...9
> 0..<9
> 0>..9
> 0>.<9
>
> Because the intention is produce a number bigger than 0 (start). So greater
> than zero less than nine.

That's not typically how it's written in math. When x is between two
values a and b, it's written a < x < b. The pointy end of the symbol
faces the smaller value. Here, 0 is the smaller value, so the pointy
end must face it, as in `0 <.. 9` and `0 <.< 9`.

>
>
>
>
> Em sex, 8 de abr de 2016 22:50, Michel Fortin via swift-evolution
> <swift-evolution at swift.org> escreveu:
>>
>> Le 8 avr. 2016 à 14:37, Erica Sadun via swift-evolution
>> <swift-evolution at swift.org> a écrit :
>> >
>> > (0 ... 9).striding(by: -2) == [9, 7, 5, 3, 1]
>>
>> The above reads wrong to me. The expression has to be read differently
>> depending on the tinny detail that is the sign of the step that comes last:
>>
>> * positive step: from 0 to 9 striding by 2
>> * negative step: to 0 from 9 striding by -2
>>
>> Am I the only one thinking it's a bit too clever to swap the start and
>> stop parts like this?
>>
>> --
>> Michel Fortin
>> https://michelf.ca
>>
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