Brian McNamara wrote:
On Mon, Feb 02, 2004 at 11:50:45PM -0800, Rich Sposato wrote:
The containers are called flex_set, flex_map, flex_multiset, and flex_multimap. They are similar to the 4 STL associative containers. There are two important differences between the STL containers and these: 1. You can search on any type that is comparable to the key_type, rather than just the key_type. (The STL associative containers only allows searches on the same type as the key.) 2. You do *not* need to create a temporary object of key_type to search through the containers. (The STL containers require you to create one temporary object to search for another.)
A good idea. I recall wishing for something like this a while ago; I don't remember if it stemmed from an actual problem in practice or just general unhappiness with the std:: interface in theory.
I had difficulty storing and finding boost::intrusive_ptr<> in std::set<>. When I wanted to check if an arbitrary pointer value was in that set like: struct some {/*...*/}; typedef boost::intrusive_ptr<some> some_ptr; typedef std::set<some_ptr> some_set; some_set set; bool exists(some const* s) { return set.find(s) != set.end(); } void foo() { bool b = exists(reinterpret_cast<some*>(0xdeadbeaf)); // boom } as std::set::find() requires a key value, it ended up with constructing the smart pointer from a bogus value trying to do add_ref() and then release() on that value which led to runtime errors. If std::set<> had been able to use not a key value for find() but a key comparable value I would not have had any problems with that code. -- Maxim Yegorushkin MetaCommunications Engineering http://www.meta-comm.com/engineering/