want a container which index the elements and whose element is writable

[breadbread1984]

I want a container which can be indexed by a member field and whose other member fields can be modified. I have tried set and found that the element retrieved from the container is readonly version of the element.
for example

set<some_class> s;
//...
set<some_class>::iterator it = s.find(obj);

the element desinated by iterator it is rea donly.
Is there one in STL or boost. Thanks for any recommendation;

[kbw]

It's not read-only, you're probably modifying a copy of the content.

You may want to try a map, it's a dictionary implmentation with an index of your choosing.

e.g.
struct User
{
    int uid;
    int gid;
    std::string name;
    std::string shell;
};

typedef std::map<int, User> Users;  // map uid to User
Users users;
//...

// change the name of uid 7;
Users::iterator p = users.find(7);
if (p != users.end)
    p->name = "Seven";