Re: [boost] [variant]compile-time-checked boost::get<T>?

Subject: Re: [boost] [variant]compile-time-checked boost::get<T>?
From: Joe Gottman (jgottman_at_[hidden])
Date: 2008-12-11 00:07:33

Steven Watanabe wrote:
> AMDG
> 
> Joe Gottman wrote:
>> Mathias Gaunard wrote:
>>> Arno Schödl wrote:
>>>
>>>> As a further extension, boost::get<S> where S is a base class of a T 
>>>> contained in the variant, should also work. I believe this would 
>>>> also be implementable with enable_if/disable_if, but we have not 
>>>> done it, so no guarantee.
>>>
>>> Actually, it should work with all types that are convertible from any 
>>> of the types of the variant.
>>>
>>
>>    Would it work for a type that is convertible from two or more of 
>> the types of the variant?
> 
> It had better not compile in that case, unless one of the types is a 
> better match
> than the rest.

    What's so dangerous about it compiling in that case?  What's wrong 
with having get<S> convert the actual underlying object of the current 
Variant to S& (or possibly const S &) if possible, and throwing an 
exception otherwise?

Joe Gottman