Let's say i have a hierarchy of object that all inherits from a abse class called base_impl. Among those classes, most of them are tempalte that have large, complex type. My idea was to use boost::any to store any of this classes' instances, any_cast them back to base_impl* and call one of the base_impl virtual method. Basically I did this :   struct expression_impl   {     virtual ~expression_impl() {}     virtual void evaluate() const = 0;   };   struct expression   {     template<class T> expression( T const& x ) : mExpr(x) {}     void evaluate() { boost::any_cast<expression_impl*>(mExpr)->evaluate(); }     boost::any mExpr;   }; Alas this fails in a bad_any_cast exception. Considering that the basic use case of expression is : expression e = /some_function_making_emporary_base_impl_instance(); I can't rely on stroing a pointer in the boost::any member. Any solution to this problem or am I doing something wrong.