DIP 57: static foreach

[Timon Gehr via Digitalmars-d]

On 11/04/2015 12:39 AM, Daniel N wrote:
> On Wednesday, 26 March 2014 at 22:14:44 UTC, Timon Gehr wrote:
>> On 03/26/2014 01:33 PM, bearophile wrote:
>>> Timon Geh:
>>>
>>>> http://wiki.dlang.org/DIP57/
>>>>
>>>> Thoughts?
>>>
>>> Is it good to support this syntax too?
>>>
>>> static foreach (enum i; 0 .. 10) {}
>>>
>>> Bye,
>>> bearophile
>>
>> Yes, I think so.
>>
>> I'll try to finish the DIP this weekend.
>
> template DIP(Args...)
> {
>    static foreach(alias a ; Args)
>    {
>    }
> }
>
> Would supporting 'alias' conflate too much into one DIP?
>

The DIP would allow:

template DIP(Args...){
     static foreach(a;Args){}
}

This has the semantics you want.

This is identical to the existing Seq-foreach:

auto foo(Args...)(){
     foreach(a;Args){
         pragma(msg,a.stringof);
     }
}

void main(){
     foo!(1,"2",main,int)();
}

In this sense, the syntax seems redundant, but if it is introduced, it 
should also be allowed for Seq-foreach. (I think this should also be the 
case for enum loop variabes as proposed by bearophile.)

I have updated the DIP draft according to those considerations, but I'm 
not sure whether 'alias' should be kept or not.

(Also, probably, using 'alias' or 'enum' on a loop variable for a 
non-seq foreach should automatically turn it into a seq foreach, but I'm 
not sure this is within the scope of the DIP.)