Re: [Boost-users] variant visitor using SFINAE problem

Subject: Re: [Boost-users] variant visitor using SFINAE problem
From: Igor R (boost.lists_at_[hidden])
Date: 2013-05-26 09:20:54

>> What visit() overload did you intend to call for vector<int>? Note
>> that enable_if condition:
>>          mpl::and_<
>>              boost::has_range_const_iterator<VisitableT>,
>>              boost::is_void<typename VisitorT::result_type>
>>          >,
>>
>> seems to be fulfilled for vector<int> case, doesn't it? But it's
>> obviously not the right overload, as int is not variant.
>
>
> thank you, you did point out it; unfortunately, my extension doesn't
> compile.

Because you actually should apply is_variant metafunction to the
value_type of the container, not to the container itself:
            mpl::not_<is_variant<typename VisitableT::value_type> >,
<....>
            is_variant<typename VisitableT::value_type>,

HTH,

Igor'.