Voldemort command structures

[Gor Gyolchanyan]

Sure. The whole point of this scheme is to specify the parameters
first, and then choose the method to call. This can lead to cool
results because the subsequent choice of the method can be deferred to
later and/or automated and/or chained with more pre-parametrized
calls. You'll be able to keep asking for more parameters by checking
them each time and finally call the method once you actually decided,
that these are enough.

On Tue, Apr 24, 2012 at 12:31 PM, CTFE-4-the-win <CTFE at 4the.win> wrote:
> On Sunday, 22 April 2012 at 18:42:19 UTC, Brad Anderson wrote:
>>
>> On Sun, Apr 22, 2012 at 4:24 AM, Gor Gyolchanyan <
>> gor.f.gyolchanyan at gmail.com> wrote:
>>
>>> Voldemort types (coined by Andrei Alexandrescu) are types, which can't
>>> be named. Like so:
>>>
>>> auto getMisteriousData(int i)
>>> {
>>>   struct Mysterious
>>>   {
>>>       int i;
>>>   }
>>>
>>>   return Mysterious(i);
>>> }
>>>
>>> The only way to use mysterious structure is to either do this:
>>>
>>> auto m = getMysteriousData(12);
>>>
>>> or
>>>
>>> ReturnTypeOf!getMysteriousData m;
>>>
>>> Here's a very handsome use case of this setup:
>>>
>>> class Set(T)
>>> {
>>> public:
>>>   auto opIndex(T datum_)
>>>   {
>>>       struct Command
>>>       {
>>>       public:
>>>           alias _datum this;
>>>
>>>           bool contains() @property
>>>           {
>>>               return (_datum in _set) !is null;
>>>           }
>>>
>>>           void add()
>>>           {
>>>               _set._data[_datum] = false;
>>>           }
>>>
>>>           void remove()
>>>           {
>>>               _set._data.remove(_datum);
>>>           }
>>>
>>>       private:
>>>           Set _set;
>>>           T _datum;
>>>       }
>>>   }
>>>
>>> private:
>>>  bool[T] _data;
>>> }
>>>
>>> this will allow you do use Set class like this:
>>>
>>> auto s = new Set!int;
>>> assert(!s[6].contains);
>>> s[6].add();
>>> assert(s[6].contains);
>>> s[6].remove();
>>> assert(!s[6].contains);
>>>
>>> This will get even better if the voldemort Command structure, returned
>>> by opIndex would include the same pattern, allowing to chain the
>>> parameters and actions in any way desirable.
>>>
>>> --
>>> Bye,
>>> Gor Gyolchanyan.
>>>
>>
>> That's really neat.  We need to start making a catalog of interesting
>> stuff
>> you can do in D.
>>
>> Regards,
>> Brad Anderson
>
>
> Be sure to add support for this also in the example:
>
> if(auto e = s[6]) // implicit contains
>  e.remove();
>



-- 
Bye,
Gor Gyolchanyan.