DIP 1020--Named Parameters--Community Review Round 2
rikki cattermole
rikki at cattermole.co.nz
Thu Sep 12 18:21:50 UTC 2019
On 13/09/2019 6:00 AM, Yuxuan Shui wrote:
> On Thursday, 12 September 2019 at 14:36:09 UTC, rikki cattermole wrote:
>> On 13/09/2019 1:44 AM, Yuxuan Shui wrote:
>>> On Thursday, 12 September 2019 at 12:06:47 UTC, rikki cattermole wrote:
>>>> On 12/09/2019 11:50 PM, Yuxuan Shui wrote:
>>>>> On Thursday, 12 September 2019 at 11:46:46 UTC, rikki cattermole
>>>>> wrote:
>>>>>> [...]
>>>>>
>>>>> Ah, sorry. I meant to write draw(shape: someShape).
>>>>
>>>> In that case, two methods:
>>>>
>>>> 1. void draw(Shape)(@named Shape shape) { draw(shape); }
>>>>
>>>> 2. void draw(Shape:Circle)(@named Shape shape) { draw(shape); }
>>>>
>>>> The second is better because of validating the parameter type, but
>>>> does require one per type. Assuming I remember this particular bit
>>>> of templates correctly.
>>>>
>>>> I had to assume that drawing has to be specific to the type passed
>>>> in and that the draw function will be concrete (can be virtual). But
>>>> that shouldn't be a problem.
>>>
>>> Sorry, I don't think I understand your answer. My question has
>>> nothing to do with templates.
>>
>> To get the functionality you asked about, I had to use templates.
>>
>> To support overloading on named parameters would require invasive
>> changes and adding a new mangling sequence. Things I want to avoid.
>>
>> a11e99z asked a similar question under your own in this part of the
>> thread tree. Same answer.
>
> No, I am not asking for overloading based on name. The two functions are
> clearly distinct based purely on parameter types.
>
> I think this basically means you cannot create functions with only
> @named parameters. I consider this a pretty serious limitation.
You can create functions with just @named parameters, but you can't use
overloading with them.
Its a side effect of not touching symbol+overload resolution.
Keep in mind that the syntax:
void draw(Shape:Circle)(@named Shape shape)
will allow you to have multiple functions named the same thing with
@named parameters. So its not as serious as it may first seem IMO.
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