Visitor pattern revisited in D

[deadalnix]

Le 27/08/2012 18:02, Michal Minich a écrit :
> On Monday, 27 August 2012 at 15:00:11 UTC, deadalnix wrote:
>> /!\ Shameless autopromotion incoming /!\
>>
>> I have recently put some effort into exploring alternatives to visitor
>> pattern and see what can be done in D. I ended up with a solution
>> which is a real improvement compared to plein old visitor pattern and
>> wanted to share this here.
>>
>> I think this is short enough to be a good example to show what can be
>> done with D capabilities.
>>
>> http://www.deadalnix.me/2012/08/25/visitor-pattern-revisited-in-d/
>
> This is nice use of d magic. If the implementation could recompute the
> functions pointers during compilation, this seems as nice generally
> function. This makes me thing of computed goto (to functions)
>
> One possibility to achieve this result for visitor is to use mixin.
>
> I would mixin implementation of accept method into very node super
> class. This is to avoid code duplication.
>
> Secondly, I would mixin implementation of opDispatch that simply does
> nothing/throws to every implementation of visitor. This is to avoid
> empty implementations of visit methods which are not needed for
> particular visitor.

This can only work if you know all node type by advance. Which is one 
limitation of the visitor pattern I intended to solve.