[swift-evolution] Change `repeat` to loop indefinitely if no while clause is present

[Xiaodi Wu]

On Tue, May 10, 2016 at 4:57 PM, Tyler Cloutier <cloutiertyler at aol.com>
wrote:

>
> On May 10, 2016, at 2:50 PM, Xiaodi Wu <xiaodi.wu at gmail.com> wrote:
>
>
>
> On Tue, May 10, 2016 at 4:46 PM, Tyler Cloutier <cloutiertyler at aol.com>
> wrote:
>
>>
>> On May 10, 2016, at 2:34 PM, Xiaodi Wu <xiaodi.wu at gmail.com> wrote:
>>
>> I think, on the contrary, it's missing the point utterly. It's up to
>> those proposing a new feature to justify its addition in light of what's
>> already here, and it's up to those proposing the removal of a feature to
>> justify why it should be removed.
>>
>> Certainly no one is proposing the removal of the while loop. Currently,
>> the One Obvious Way of making an infinite loop is `while true`, and it is
>> up to the proponents to advance a reason why a replacement would be
>> superior. I cannot think of a greater non-sequitur than supplying a
>> demonstration of why while loops are useful.
>>
>>
>> That’s what I am saying. No one is supplying a demonstration of why while
>> loops are useful and that suggestion is a straw man.
>>
>
> That was not meant to be a straw man, not on my part. It is my
> understanding of Harlan's example. It shows that, without while loops, it
> is unwieldy to express the same thing using goto statements. That is fine,
> but it is not at all on point for this discussion.
>
>
>> My point below that simple and clear syntax is an improvement on syntax
>> with more noise.
>>
>> repeat {
>> // code
>> }
>>
>> vs
>>
>> repeat {
>> // code
>> } while true
>>
>
> What's wrong with `while true { }` ?
>
>
> This is a good question. In my opinion, nothing in and of itself, however
> since repeat is part of the language and it has a stand alone meaning in
> english,
>

"Repeat" in English does not mean "do something forever." It means "do
something one more time."


> it stands to reason that users will expect that it can stand alone just as
> do { } does. I would love to hear if this is a sentiment I alone have, or
> if others feel the same.
>
>
> The reason that the former is superior to the latter is that, given repeat
>> is already part of the language, the former it is simpler, with less noise.
>> It reads like simple english. It also aligns well with current do {}
>> syntax. This is the only argument I’m offering, and I think it’s the only
>> one that could be offered for such a small syntax change given that it
>> *only* serves to clarify and reduce noise of current syntax which has the
>> same functionality.
>>
>>
>> On Tue, May 10, 2016 at 16:27 Tyler Cloutier via swift-evolution <
>> swift-evolution at swift.org> wrote:
>>
>>> On May 10, 2016, at 2:13 PM, Harlan Haskins via swift-evolution <
>>> swift-evolution at swift.org> wrote:
>>>
>>> You could always do your control flow with goto’s anyway…
>>>
>>> func foo() {
>>>   var i = 0
>>>   func goto(_ label: String = "entry") {
>>>     switch label {
>>>     case "entry":
>>>       print("beginning loop…")
>>>       goto("cond")
>>>     case "cond":
>>>       goto(i < 10 ? "body" : "end")
>>>     case "body":
>>>       i += 1
>>>       print("\(i)")
>>>       goto("cond")
>>>     case "end":
>>>       break
>>>     default: break
>>>     }
>>>   }
>>>   goto()
>>> }
>>>
>>> Apologies,
>>> Harlan
>>>
>>>
>>>
>>> And isn’t this the point really. Yes there are many different ways of
>>> doing something, but there should be one obvious way. IMHO, there is
>>> nothing more obvious than just
>>>
>>> repeat {
>>>
>>> }
>>>
>>> It’s very clear. It’s not about adding complex control flow, it’s about
>>> simplifying current syntax. I don’t think anyone is arguing that it’s more
>>> powerful than what while loops currently offer.
>>>
>>>
>>>
>>> On May 10, 2016, at 2:05 PM, Taras Zakharko via swift-evolution <
>>> swift-evolution at swift.org> wrote:
>>>
>>> When I need a loop with complex control flow that does not fit into the
>>> classical while {} or repeat {} while structure, I use this:
>>>
>>> do_stuff: do {
>>>  …
>>>  continue do_stuff
>>> }
>>>
>>> This pattern explicit and allows very complex control flow patterns
>>> without the drawbacks of the unrestricted goto construct.
>>>
>>> Therefore I don’t see utility with having a repeat {} without while
>>> clause.
>>>
>>> Best,
>>>
>>> Taras
>>>
>>>
>>> On 10 May 2016, at 22:39, Dominik Pich via swift-evolution <
>>> swift-evolution at swift.org> wrote:
>>>
>>>
>>> On May 10, 2016, at 3:30 PM, Tyler Cloutier via swift-evolution <
>>> swift-evolution at swift.org> wrote:
>>>
>>> Secondly it’s a very simple way of introducing new programmers to loops.
>>> It’s IMHO more clear to a new programmer that repeat will just repeat
>>> indefinitely vs while true.
>>>
>>>
>>> This point seems strange to me - why teach a new programmer about loops
>>> by first showing them a looping construct they should probably never use in
>>> actual practice until they really know what they’re doing?
>>>
>>> totally agree… it would be a bad first introduction, id say :)
>>>
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>>
>>
>
>
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