I have a map<string,any> that I would like to control access to so that if a pointer is put in the map, only a const pointer can be extracted. The following simple code illustrates the situation. //-------------------- <snip> -------------------------- typedef std::map<std::string,boost::any> Properties; template<typename T> void set( Properties& p, const std::string name, const T t ) { p[name] = t; } template<typename T> const T get( const Properties& p, const std::string name ) { const Properties::const_iterator iprop=p.find(name); try{ const T t = boost::any_cast<const T>(iprop->second); return t; } catch(const boost::bad_any_cast &){ throw std::runtime_error("bad cast"); } } int main() { Properties p; int i=1; set(p,"int",i); set(p,"int*",&i); int* j = get<int*>(p,"int*"); // I don't want this to compile const int* k = get<int*>(p,"int*"); // I want this to compile fine. } //-------------------- </snip> ------------------------- Currently this whole code compiles without trouble, but I don't want to allow a non-const pointer to be extracted. Any ideas of how to accomplish this? Thanks for any tips!