Re: [boost] [variant] assign and access the assigned value simultaneously

Subject: Re: [boost] [variant] assign and access the assigned value simultaneously
From: feverzsj (feverzsj_at_[hidden])
Date: 2014-03-28 13:21:52

hi list,
   Let me explain this in more detail.
   Say, if one want to renew an object of some type which may be hold by a
variant, and not care about the object's old data, he may do somthing like:
       
       // assure variant hold object of type T
       if(var.which() != T's index)
             var = T();                           // 2 visitation + copy
       T& t = boost::get<T>(var);     // 1 visitation
       // process t

   If we have T& t = var.assign(T()), 1 visitation can be eliminated.
   If we have T& t = var.construct<T>(...), only 1 visitation and optionally
1 in place construction are needed.

regars.

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