Re: [boost] [RFC] Generic non-intrusive Visitor pattern utility

From: Tobias Schwinger (tschwinger_at_[hidden])
Date: 2008-01-11 12:37:29

dizzy wrote:
> Hello
> 
> On Friday 11 January 2008 15:47:59 Tobias Schwinger wrote:
>> dizzy wrote:
>>> I would like to know if boost implements something similar
>> I just skimmed your post very quicky, but it seems you might perhaps
>> want to read this thread:
>>
>>      http://permalink.gmane.org/gmane.comp.lib.boost.user/27516
> 
> Thanks for your link, it was an interesting read (along with the referenced 
> article). It appears this if-istype/else technique is widely employed when 
> needing a non-intrusive Visitor, when one cannot modify original hierarchy 
> API (even tho I can modify it I still prefer the nonintrusive version as I 
> find the action of needing to visit the hierarchy a decision of the user and 
> not a feature for the hierarchy to provide it).
> 
> So the logic of finding the type liniarly can be rewritten in my code to use 
> boost::mpl features as from the link provided. Even so, if boost does not 
> have such a generic Visitor feature, wouldn't it be a good addition?

Honestly, I find its practical value rather questionable.

 From where I stand, the need for such a thing does most likely indicate 
that inheritance is probably used in a place where it shouldn't.

Regards,
Tobias