> On 1 Feb 2017, at 18:29, Chris Davis via swift-evolution
> <[email protected]> wrote:
>
> ah! I forgot about the break semantics, that’s definitely one for the con
> list.
>
> I like Nicolas’ solution, clear to read.
>
>> On 1 Feb 2017, at 18:18, Nicolas Fezans <[email protected]> wrote:
>>
>> I tend to write this kind of treatment the other way around...
>>
>> if names.isEmpty {
>> // do whatever
>> } // on other cases I might have a few else-if to treat other cases that
>> need special treament
>> else {
>> for name in names {
>> // do your thing
>> }
>> }
>>
This only works if you know the size of the sequence before you start iterating
it. You can, for example, iterate a lazy sequence and calculating its size
before iterating it defeats the object.Thus for { … } else { … } where the else
block only executes if the for block was never executed does have some utility.
However, I am not in favour adding it. The same functionality can be achieved
by counting the number of iterations and testing the count afterwards (or by
using a boolean). It takes a couple of extra lines of code and an extra
variable, but I think that is a Good Thing. It’s more explicit and (as the
Python example shows) there could be hidden subtleties that confuse people if
for … else … is badly designed. Also, in many cases, I would argue that
treating the zero element sequence differently to the n > 0 element sequence is
a code smell. About the only use-case I can think of off the top of my head is
UI presentation e.g. “your search didn’t return any results” instead of a blank
page.
Talking of Python, Swift is not Python and the argument not to implement a
feature because its semantics conflict with the semantics of a similar looking
feature in another language is bogus. I don’t see the Python for … else being
different (and having looked it up to see what you all were talking about, my
opinion is that the Python for … else is a disaster) as being a legitimate con
to this cleaner and more logical idea in Swift.
>>
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