> On 23 Mar 2016, at 14:55, Jeremy Pereira via swift-evolution
> <[email protected]> wrote:
>
>
>> On 23 Mar 2016, at 11:38, Brent Royal-Gordon <[email protected]> wrote:
>>
>>> One advantage of the old C style for loop is that everything to do with
>>> loop control is in one place, usually on one line. There is currently no
>>> way of doing that for the (quite common) use case of iterating through a
>>> sequence until a particular condition (other than the end of the sequence)
>>> is true except by using a break.
>>
>> If you can stand using method chains, I believe that role would be filled by
>> the `takeWhile(_:)` method that Kevin Ballard (IIRC) wants to add to
>> Sequence. (Although `takeWhile(_:)` would be greedy by default.)
>
> After writing the last email, I tried adding a method to SequenceType called
> whileTrue(_:) that did pretty much the same thing. It wrapped a Generator in
> another custom Generator that ended when the supplied closure returned true
> and it worked fine. However, the closure had no visibility of the iterator so
>
> for i in someIntegerSequence.whileTrue({ i < 5 }) { … }
>
> was understandably a compiler error.
>
>>
>> But honestly, other than distaste, I don't see much of a practical issue
>> with putting an `if` or `guard` on the first line with a `break` in it. That
>> still clusters the iteration logic at the top of the loop, even if it's not
>> quite in a single statement.
>
> True, but we could have argued the same about the `where` keyword and that is
> in existence. :-)
Speaking of where, why wouldn’t you just do:
for eachElement in theIntegerSequence where eachElement < 5 { … }
I think simplified striding is really all we need to cover c-style loop
replacement, the only case that can’t be covered is one that uses some kind of
variable stride amount, i.e- replacing:
var step = 0
for (var i = 0; i < 100; i += step) { step += 1 }
But I think that’s unusual enough that it doesn’t really matter._______________________________________________
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