Re: [Boost-users] [variant] how to get 1st bounded type

Why don't you like visitor to dispatch the type stored in the variant?

I like it very much, and I use variant because of the power of the static visiting mechanism. The reason I wanted to test if the variant contains its 1st type is the following: my variant is made of a list of shared-pointers to various types; there's a routine that initializes it with one of the types depending on some conditions, then it applies some visitor on the resulting variant and stores it then in a container - however, there's no "default" behavior, so if neither condition was met, the variant remains "uninitialized" - i.e. it contains 1st type "zero" ptr. I want neither apply the visitor on "empty" smartpointer nor store it in the container, so I have to know whether it was "really" created or not. Two simple ways I can think about are to test the resulting variant or to introduce some flag - of course, both ways are far from ideal... struct my_visitor { typedef bool return_type; vector & vec_; my_visitor (vector & vec) : vec_(vec) {} my_visitor (my_visitor & other) : vec_(other.vec_) {} bool opeator()(...) {return false;} bool operator()(type1 value) { vec_.push_back(variant_type(value)); } bool operator()(type2 value) { vec_.push_back(variant_type(value)); } } :boost::apply_visitor(my_visitor(my_vec), my_variant)