[swift-evolution] Revisiting 0004 etc. - Swift deprecations

Goffredo Marocchi panajev at gmail.com
Sun Apr 3 04:36:36 CDT 2016

It would be very interesting to see more examples dynamic loop conditions and dynamic loop increments using the Swifter for in loop with strides... without while :).

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> On 3 Apr 2016, at 09:19, Xiaodi Wu via swift-evolution <swift-evolution at swift.org> wrote:
> On Sat, Apr 2, 2016 at 6:45 PM, John Heerema via swift-evolution
> <swift-evolution at swift.org> wrote:
>> Yes, there are many cases in which I believe that Swift
>> provides looping structures that are safer and easier to understand than
>> the
>> C-style For loop. I¹d even say most cases. But I work in the scientific and
>> engineering domains, and can point to many instances of looping structures
>> that
>> are easily expressed with a C-style For loop, but are clumsy to implement
>> without it.
>> In the world of the natural sciences, there are any number
>> of instances of loop increments that requires some kind of a calculation.
>> There
>> are any number of instances of dynamically calculated loop termination.
>> Swift¹s stride has some nice features for simple increments,
>> but also has some important limitations. Among them, it involves the two
>> step
>> process of first creating an enumerable set, and then iterating over it.
>> In the
>> natural sciences, it is not uncommon for complex loop increments to be
>> used in
>> loops that are executed millions of times.
>> Conceptually, creating an enumerable set, and then iterating over it,
>> reeks of the arrogance of assuming that computing resources are unlimited.
>> Even
>> though the compiler may optimize the stride into the loop structure, it
>> feels
>> like unnecessarily creating a gigantic enumerable set.
>> Whether we like it or not, the enduring popularity of the
>> C-style For loop comes from it¹s flexibility. Swift doesn¹t have a better
>> alternative that also provides the same flexibility. So don¹t take it
>> away. If
>> you don¹t like it (I don¹t always either), think of something that is
>> clearly
>> superior in 100% of use cases. Even then, I would argue against removing
>> it.
> FWIW, as an anecdote, I've been working on a side project in the
> natural sciences using Swift and I haven't missed the C-style for;;
> loop much. It seemed a little irksome at first to refactor, but that
> was about it. Looking around at other languages, I'm also not seeing
> evidence that working in the natural sciences domain
> disproportionately requires these loops. For instance, Python (which
> has significant uptake in my corner of the natural sciences world) and
> Julia (the up-and-coming technical computing language) both lack
> C-style for;; syntax and the ++ and -- operators, which doesn't seem
> to have dampened the enthusiasm of my colleagues for those languages.
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