Flag proposal

[Andrei Alexandrescu]

On 6/11/11 8:25 AM, Michel Fortin wrote:
> On 2011-06-11 09:05:52 -0400, "Steven Schveighoffer"
> <schveiguy at yahoo.com> said:
>
>> As far as the negation, I think we need one more layer of type:
>>
>> struct FlagParam(string pname)
>> {
>> Flag!pname value;
>> alias value this;
>> this(Flag!pname x) { this.value = x }
>> FlagParam op???() const { return FlagParam(cast(Flag!pname)!value); }
>> }
>>
>> BTW, is there a way to hook "!"? Maybe this won't work... The idea is
>> to have Yes.abc return FlagParam!"abc"(Flag!"abc".yes).
>
> If you need to convert a bool to a Flag!"abc", you can do any of these:
>
> func(expression ? Yes.abc : No.abc);
>
> or
>
> func(cast(Flag!"abc")expression);
>
> or, with your proposal:
>
> func(FlagParam!"abc"(expression));
>
> None of this is very appealing, but I find the first is the most readable.

Agreed. I'll venture to add that I find the first also more desirable 
than an implicit conversion from func(expression).

Andrei