Re: [boost] [any] interest in boost::variant style visitors for boost::any?

From: Steven Watanabe (steven_at_[hidden])
Date: 2006-12-14 20:36:57

AMDG

"Korcan Hussein" wrote:
> "Steven Watanabe " wrote:
>   
>> >Do you intend to make boost::any a typedef then?
>>     
> That would do it unless there is some non-obvious ambiguity that this 
> may cause.

Not that I know of.

> Basically what i meant was you have 4 cases of: cosntant visitor 
> visits constant and non-constant visitee non-constant visitor visits 
> constant and non-constant visitee constant visitee accepts cosntant & 
> non-constant visitor non-constant visitee accepts cosntant & 
> non-constant visitor

Ok.

>> >For this last I don't think there is a good non-intrusive solution.
>>     
> Are you talking about the complete solution or catch-all part? i don't 
> see exactly how this is an intrusive solution so please elaborate/clarify.

It isn't.  I was thinking specifically about dynamic_any.

>> >If the default is to throw an exception then it effectively limits the 
>> >contained type to those enumerated. In this case it is probably better to 
>> >use variant in the first place.
>>     
> I don't see what the problem is since a user can override the default 
> or later extend there original visitor to support new (set) type(s), 
> as well as override the definition of the old supported types if 
> he/she wishes.

I don't quite understand.  Would I extend it statically or dynamically?

> This solution seems to be much better than type casting (for every 
> type wanted) & type switching code that you have to do with 
> boost::any::. If no one likes the idea of a default catch-all/generic 
> visit and have a better alternative then i'm open to it since this 
> isn't set in stone and isn't diffcult to change since the 
> implementation is so trivial :) Actually when i think about it the 
> "catch-all" isn't even really need/necessary, the original reason why 
> i put it in in the first place was as a constrast to generic visits of 
> with boost::variant visitors. 

You still need a catch-all even if it is not exposed to the user, don't you?

> Anyways it looks as if no one is interested, even just to make a 
> comment of any form :( Thanks Korcan Hussien.

In Christ,
Steven Watanabe