Oop! sorry, I did not intend to send that yet -- I was toying with the problem discussed in this thread but my finger slipped.. :( ________________________________ From: John Femiani Sent: Wednesday, May 07, 2008 2:53 AM To: 'boost-users@lists.boost.org' Subject: 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<variant_type> & vec_; my_visitor (vector<variant_type> & 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)); return true; } bool operator()(type2 value) { vec_.push_back(variant_type(value)); return true; } } vector<variant_type> my_vec :boost::apply_visitor(my_visitor(my_vec), my_variant)