Hi,

In the "show what can be done, not what should be done" category, someone has done a C++ version of Hello World using the up-coming metaclass stuff:

https://twitter.com/Cor3ntin/status/1127210941718962177

I immediately (once I knew about it) replied with the Python version:

https://twitter.com/russel_winder/status/1127859587393163265


   class Hello: pass

   World = None

   if __name__ == '__main__':
       print(" ".join([item for item in dir() if not item.startswith("_")]))


but clearly a better competitor would be a D version. Anyone done this sort of thing, i.e. compile time metaclass manipulation?


-- 
Russel.
===========================================
Dr Russel Winder      t: +44 20 7585 2200
41 Buckmaster Road    m: +44 7770 465 077
London SW11 1EN, UK   w: www.russel.org.uk

On Monday, 13 May 2019 at 09:06:07 UTC, Russel Winder wrote:
> Hi,
>
> In the "show what can be done, not what should be done" category, someone has done a C++ version of Hello World using the up-coming metaclass stuff:
>
> https://twitter.com/Cor3ntin/status/1127210941718962177
>
> I immediately (once I knew about it) replied with the Python version:
>
> https://twitter.com/russel_winder/status/1127859587393163265
>
>
>    class Hello: pass
>
>    World = None
>
>    if __name__ == '__main__':
>        print(" ".join([item for item in dir() if not item.startswith("_")]))
>
>
> but clearly a better competitor would be a D version. Anyone done this sort of thing, i.e. compile time metaclass manipulation?

Something like this is possible (for a long time now, I think...),

´´´
import std.format;
struct Hello;
int World;

pragma(msg, format!"%s %s"(__traits(allMembers, mixin(__MODULE__))[$-2 .. $]));
´´´

but I'm sure, more cool versions are possible ;)

On 5/13/19 10:06 AM, Russel Winder wrote:
> Hi,
> 
> In the "show what can be done, not what should be done" category,
> someone has done a C++ version of Hello World using the up-coming
> metaclass stuff:
> 
> https://twitter.com/Cor3ntin/status/1127210941718962177
> 
> I immediately (once I knew about it) replied with the Python version:
> 
> https://twitter.com/russel_winder/status/1127859587393163265
> 
> 
>     class Hello: pass
> 
>     World = None
> 
>     if __name__ == '__main__':
>         print(" ".join([item for item in dir() if not item.startswith("_")]))
> 
> 
> but clearly a better competitor would be a D version. Anyone done this
> sort of thing, i.e. compile time metaclass manipulation?

I replied with a no-brainer equivalent.

On 5/13/19 11:25 AM, Alex wrote:
> On Monday, 13 May 2019 at 09:06:07 UTC, Russel Winder wrote:
>> Hi,
>>
>> In the "show what can be done, not what should be done" category, someone has done a C++ version of Hello World using the up-coming metaclass stuff:
>>
>> https://twitter.com/Cor3ntin/status/1127210941718962177
>>
>> I immediately (once I knew about it) replied with the Python version:
>>
>> https://twitter.com/russel_winder/status/1127859587393163265
>>
>>
>>    class Hello: pass
>>
>>    World = None
>>
>>    if __name__ == '__main__':
>>        print(" ".join([item for item in dir() if not item.startswith("_")]))
>>
>>
>> but clearly a better competitor would be a D version. Anyone done this sort of thing, i.e. compile time metaclass manipulation?
> 
> Something like this is possible (for a long time now, I think...),
> 
> ´´´
> import std.format;
> struct Hello;
> int World;
> 
> pragma(msg, format!"%s %s"(__traits(allMembers, mixin(__MODULE__))[$-2 .. $]));
> ´´´
> 
> but I'm sure, more cool versions are possible ;)

The idea is to just provide something simple that doesn't introduce a bunch of stuff. Here's what I wrote:

https://twitter.com/incomputable/status/1127891251666223105