[swift-evolution] [Idea] Passing an Array to Variadic Functions

[Justin Jia]

Ah thanks! I forgot to select the Reply All option. 

My first email:

>> Maybe you can check it out:
>> 
>> https://github.com/JustinJiaDev/SwiftShell
>> 
>> I prefer to write ls(.all, .longFormat) instead of ls([.all, .longFormat]). The former one looks a lot nicer. And it is much easier to type. This is important if I want to use it as a shell. 

Dennis's reply:

> Hey Justin, you didn’t include the list, if you want to keep your mail private: perfect, if not: now you know it :)
> 
> Regarding your example:
> 
> I think that’s a pretty good use case for an OptionSetType (which, unfortunately for you, leads to the same syntax you dislike [without the dot in front of the identifier]).
> And remember that you can still overload the functions (having different numbers of arguments) :)
> 
> - Dennis


I didn't realize that I can use OptionalSetType. Thanks for pointing it out! But I chose to use enum is because of the auto completion. I can see the list of options after I enter the leading dot. 

It's a experimental project. But my point is: Swift is very safe and efficient, but at the same time it is also very flexible. Removing this feature will harm its flexibility. 

I agree that we should remove the splat behavior, c style for loop and ++ -- operators, because sometimes they will confuse people. 

e.g.

array[index++] = x;
array[++index] = x;

However, variadic functions are really easy to understand. 

For example:

sum(x)
average(x)
NSLog("%d", x)
NSString.stringWithFormat("%d", x)

Justin

> On Apr 18, 2016, at 2:13 PM, Dennis Weissmann <dennis at dennisweissmann.me> wrote:
> 
> Hey Justin, you didn’t include the list, if you want to keep your mail private: perfect, if not: now you know it :)
> 
> Regarding your example:
> 
> I think that’s a pretty good use case for an OptionSetType (which, unfortunately for you, leads to the same syntax you dislike [without the dot in front of the identifier]).
> And remember that you can still overload the functions (having different numbers of arguments) :)
> 
> - Dennis
> 
>> On Apr 18, 2016, at 11:03 PM, Justin Jia <justin.jia.developer at gmail.com> wrote:
>> 
>> Maybe you can check it out:
>> 
>> https://github.com/JustinJiaDev/SwiftShell
>> 
>> I prefer to write ls(.all, .longFormat) instead of ls([.all, .longFormat]). The former one looks a lot nicer. And it is much easier to type. This is important if I want to use it as a shell. 
>> 
>> Justin
>> 
>>> On Apr 18, 2016, at 5:55 AM, Dennis Weissmann <dennis at dennisweissmann.me> wrote:
>>> 
>>> Hm, sorry but I’m still not convinced :(
>>> 
>>> I still find it confusing and I think if it wasn’t in Swift already, it would not be added. Maybe someone can come up with a strong reason why it should be added if it weren’t there.
>>> 
>>> - Dennis
>>> 
>>>>> On Apr 18, 2016, at 10:10 AM, Gwendal Roué <gwendal.roue at gmail.com> wrote:
>>>>> 
>>>>> 
>>>>> Le 18 avr. 2016 à 10:02, Dennis Weissmann <dennis at dennisweissmann.me> a écrit :
>>>>> 
>>>>> That’s IMO already a problematic case:
>>>>> 
>>>>>> 	DatabaseTable.select(id, name).order(name, id)		// What’s the problem?
>>>>>> 	// vs.
>>>>>> 	DatabaseTable.select([id, name]).order([name, id])	// OK, of course... But some people will find it a litle short
>>>>> 
>>>>> The problem is that you can’t tell by looking at the call site whether `select` takes an id and a name as parameter (the function being declared as `func select(id: String, _ name: String)` or a vararg `func select(string: String…)`.
>>>>> Both call sites look like this:
>>>>> 
>>>>>> select(id, name)
>>>>> 
>>>>> I think it would make the language clearer and more consistent if varargs were removed.
>>>> 
>>>> Sorry my example wasn’t clear enough, and that’s why you couldn’t tell by looking at the call site what was happening. You were missing context. "id" and "name" are not values, they’re database columns. It’s more something along:
>>>> 	
>>>> 	DatabaseTable {
>>>> 		func select(columns: Column…) { … }
>>>> 	}
>>>> 	
>>>> 	people.select(idColumn, nameColumn)
>>>> 	furniture.select(nameColumn, widthColumn, heightColumn, depthColumn, priceColumn)
>>>> 
>>>> (Sometimes examples are too complex, and don't serve well their purpose - my mistake)
>>>> 
>>>> Maybe you’ll follow the counter argument now. Which is "of course a variadic function can always be turned into a function that takes an array, what a surprise, but this is not always the good thing to do."
>>>> 
>>>> Regards,
>>>> Gwendal Roué
> 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-evolution/attachments/20160418/0f864e16/attachment.html>