Flag proposal

[Andrei Alexandrescu]

On 6/10/11 1:52 PM, Robert Clipsham wrote:
> On 10/06/2011 19:06, Andrei Alexandrescu wrote:
>> On 6/10/11 12:42 PM, Robert Clipsham wrote:
>>> On 10/06/2011 17:15, Andrei Alexandrescu wrote:
>>>> https://github.com/D-Programming-Language/phobos/pull/94
>>>>
>>>> Discuss!
>>>>
>>>> Andrei
>>>
>>> I really *really* don't like this. It's ugly and verbose, and a pathetic
>>> work around for the lack of named parameters. Either support named
>>> parameters or not, don't have an ugly half-baked work-around.
>>
>> This is not half-baked. It's pretty much it.
>
> My choice of wording was poor, sorry.
>
>> Ugly is in the eye of the beholder, but I fail to see how the added
>> punctuation makes Flag!"param".yes significantly more verbose than param
>> : true.
>
> foo(param: true, otherParam: false);
> foo(Flag!"param".yes, Flag!"otherParam".no);
>
> I don't know about you, but I find the former is far more legible. I'd
> hate to see my code littered with Flag!"something".

I agree it's more legible. The crucial question is whether the added 
legibility warrants adding a new feature to the language.

>> The problem that named parameters are still optional remains. Or we need
>> to add one extra language feature to specify required named parameters.
>
> void foo(bool param, bool otherParam, bool thisOneIsntRequired = false);
>
> Call it with or without named parameters, two are required, one is not.
>
> foo(otherParam: true, param: false);
> foo(true, false);
> foo(otherParam: true, param: false, thisOneIsntRequired: true);
>
> Would all be valid.

The second call is problematic because it still allows bad style in calls.


Andrei