> On May 10, 2016, at 3:59 PM, Xiaodi Wu <[email protected]> wrote:
>
> On Tue, May 10, 2016 at 5:56 PM, Tyler Cloutier <[email protected]
> <mailto:[email protected]>> wrote:
>
>> On May 10, 2016, at 3:13 PM, Xiaodi Wu <[email protected]
>> <mailto:[email protected]>> wrote:
>>
>> On Tue, May 10, 2016 at 3:30 PM, Tyler Cloutier via swift-evolution
>> <[email protected] <mailto:[email protected]>> wrote:
>> I’d actually say that I’m strongly in favor of allowing just a repeat
>> keyword, although I wouldn’t support making 'while true’.
>>
>> Firstly it reduces clutter
>>
>> Can you explain what clutter you see? Unless I misunderstand what you're
>> referring to, reducing the 10 letters in `while true` to the six letters in
>> `repeat` is hardly "reducing clutter."
>>
>> and makes it very clear that the the code is just supposed to repeat.
>>
>> I disagree here also. It is not very clear at all that the code is supposed
>> to repeat indefinitely, not to any audience.
>>
>> First, it would not be clear to users who are experienced in Swift and aware
>> of this proposal. Code is meant to be read, and allowing the omission of a
>> trailing clause to produce two very different behaviors means that it is not
>> clear what `repeat {` means until you encounter the closing brace and check
>> for what follows. Moreover, what follows could be the keyword `while` on the
>> following line, and in that case you cannot know whether the expression that
>> follows `while` is the beginning of a new while loop until you encounter or
>> don't encounter a new opening brace. By contrast, `while true {` cannot be
>> anything other than the beginning of an infinite loop. You already know that
>> fact after reading 12 letters.
>>
>> Second, it would not be clear to users migrating from another C-family
>> language. `while true { }` is immediately understood by users of any other
>> related language.
>>
>> Third, it would not be clear based on a knowledge of English. In common use,
>> "repeat" does not mean repeat forever; it means to repeat once (i.e. do
>> something twice). If I ask you to repeat something you just said, I should
>> hope that you do not keep reciting it over and over until I tell you to stop.
>>
>> 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.
>>
>> I can speak to this a little bit, having introduced a new programmer to
>> loops very recently and having done so in the past as well. I have not
>> encountered anyone who has trouble with the *concept* of looping--i.e. the
>> idea that the same code can be run over and over.
>>
>> Where things get tricky is the difficulty of mastering the syntax of the
>> while loop and, more problematic, the syntax of the classic for;; loop.
>> Introducing a simple way to make something repeat forever does not solve
>> this learning hurdle, because students will continue to have to contend with
>> these other types of loops in order to be productive in the language. A
>> special syntax for repeating forever is especially unhelpful because it is
>> just functional enough that a discouraged student may choose to avoid
>> learning other types of loops and instead combine the infinite loop with if,
>> continue, and break.
>
> I’d also like to point out Chris’ comments on the
>
> repeat X {
>
> }
>
> discussion.
>
> “
> This is a very valid use case.
>
> FWIW, “repeat N {}” was originally designed and scoped into the Swift 2
> implementation of the feature, but was cut due to schedule limitations.
> There is precedent for this sort of feature in many teaching oriented
> languages (e.g. Logo).
>
> I’d say that the pro’s and con’s of this are:
>
> + Makes a simple case very simple, particularly important in teaching.
> + Even if you aren’t familiar with it, you can tell at first glance what the
> behavior is.
> - It is “just syntactic sugar”, which makes the language more complex.
> - It is a very narrow feature that is useful in few practical situations.
>
> -Chris
> “
>
> In this case, I would say it’s not making the language any more complex given
> that repeat-while is a current construct. Admittedly it is a very narrow
> feature, but it’s also a small one.
>
> For the reasons I outlined above, I'd be +1 for `repeat N` and -1 for this
> case.
>
That’s fair enough. :)
But surely you’ll admit that if
repeat N {
}
was valid, then repeat { } follows as the logical repeat indefinitely syntax,
no?
>
>
>>
>> Lastly, this isn’t the first time this has been brought up on this list and
>> there was previously discussion about the fact that when people see the
>> repeat keyword that it should naturally repeat indefinitely unless a where
>> clause is specified.
>>
>> I do believe that this is the first time this suggestion has been introduced
>> to the list. I do not recall any previous discussion focused on infinite
>> loops; they have been about repeating a finite number of times, using
>> proposed syntax such as `repeat 3 times { }` or variations on that theme.
>>
>> I also think the concern that an accidental infinite loop is any greater
>> than it is currently.
>>
>> Code gets refactored and edited. We're discussing on another thread changing
>> the rules about dangling commas in parameter lists for that very reason. If
>> you try to move a block of code with a repeat...while loop but accidentally
>> leave behind the last line, this syntax will cause you grief.
>>
>> Tyler
>>
>>
>>
>>> On May 10, 2016, at 1:09 PM, Erica Sadun via swift-evolution
>>> <[email protected] <mailto:[email protected]>> wrote:
>>>
>>> I do not see sufficiently measurable benefits to this proposal to add it to
>>> the language.
>>> It's easy enough to roll your own `repeatForever` function with trailing
>>> closure.
>>>
>>> I also want to thank you for bring it up on-list. Not every idea is right
>>> for Swift but it's
>>> always refreshing to see innovative thoughts added to the discussion.
>>> Please do not be
>>> discouraged by the generally negative feedback on this particular idea.
>>>
>>> -- Erica
>>>
>>>> On May 10, 2016, at 1:27 AM, Nicholas Maccharoli via swift-evolution
>>>> <[email protected] <mailto:[email protected]>> wrote:
>>>>
>>>> Swift Evolution Community,
>>>>
>>>> Currently writing an infinite loop in swift looks either something like
>>>> this:
>>>>
>>>> while true {
>>>> if ... { break }
>>>> //...
>>>> }
>>>>
>>>> Or this:
>>>>
>>>> repeat {
>>>> if ... { break }
>>>> //...
>>>> } while true
>>>>
>>>> But I think it might be best to change the syntax / behaviour of `repeat`
>>>> to loop
>>>> indefinitely if no trailing while clause is present:
>>>>
>>>> repeat {
>>>> if ... { break }
>>>> //...
>>>> }
>>>>
>>>> while still allowing a trailing `while` clause as in:
>>>>
>>>> repeat {
>>>> foo += bar
>>>> } while foo.count < limit
>>>>
>>>> I also want to propose that it should be a compile time error to use
>>>> single `Bool` constants as while loop conditions, so no more `while true {
>>>> ... }` it would become `repeat { ... }`
>>>>
>>>> I was thinking of drafting a short proposal if there was enough positive
>>>> feedback.
>>>>
>>>> How does it sound?
>>>>
>>>> - Nick
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>>>
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