[swift-evolution] [Proposal] Add keyword "by" as syntactic sugar to streamline For-In-loop

[Vladimir.S]

as @Erica just noted, we probably will have this in Swift3 :

for i in (1...10).striding(by: 3) {..}
for i in (1...10).striding(by: -3) {..}

But.. compare how the next is more clear and nice looking, has less noise, 
how faster this will be typed.. :

for i in 1...10 by 3 {...}
for i in 1...10 by -3 {...}

just beautiful :-)
My opinion: this .striding is about Range type. Range type is used in many 
places, not just in for-in loop. It is important to have handy and clear 
methods for Range. But. If we are talking about loop - why(why?) can't we 
have such a great syntax for such a common loop task? It is explicit, it 
can generate the same (1...10).striding(by: 3) code internally.
IMO I'd love to have such syntax in Swift for for-in loop

On 13.04.2016 17:52, Hans Huck via swift-evolution wrote:
> Rationale:
> Swift's For-In-loop is fine, as long as you don't need an iteration step
> size other than 1/-1, in which case it becomes unexpectedly inconsistent
> and unwieldy.
> for i in 1...10
> for i in reverse(10...1)
> for i in stride(from:1, through:10, by:3)
> or even
> for i in 1.stride(through:10, by:3)
> The above sequence is not only confusing for teaching purposes/beginners
> (first lesson: protocols. really?), but also unnecessarily bulky for
> everyday use. It's a For-loop, one of the most basic and frequently used
> structures in any language -- please let's make it pithy.
>
> Comparison:
> Currently, even the C-style For-loop we are just about to get rid of could
> be argued to be more concise and consistent, but significantly more so are
> the likes of
> # Python
> for i in range(1, 10, 3):
> -- Lua
> for i = 1, 10, 3
> ' Basic
> for i = 1 to 10 step 3
> (* Modula-2 *)
> for i := 1 to 10 by 3
> // Chapel
> for i in 1..10 by 3
> or any other remotely relevant non-C-style language that allows For-loops
> with an altered step size.
> While there are other issues like having to use reverse(1...10) instead of
> simply 10...1, (which compiles, but doesn't run, even when using literals
> -- why?) none of it goes against the grain as much as being forced to type
> out stride(boiboiboilerplate) for a simple iteration.
>
> Suggestion(s):
> A) Add keyword "by" as syntactic sugar, used as in Modula/Chapel (and tip
> our hat to Algol 68):
> // Swift
> for i in 1...10 by 3
> for i in reverse(1...10) by -3
> or even better yet (if feasible):
> B)
> for i in 1...10 by 3
> for i in 10...1 by -3
>
> Please comment, and thanks everyone for reading.
> -- Hans
>
>
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