Re: Contraints on equal_range comparison function object

For:
    template<class ForwardIterator, class T, class Compare>
    pair<ForwardIterator, ForwardIterator>
    equal_range(ForwardIterator first, ForwardIterator last, const T&
value, Compare comp);
what are the constraints on T?

The Standard only specifies that "Type T is LessThanComparable
(20.1.2)." Is that it?

The reason I am asking is because I have a case something like:
         struct Compare
         {
        bool operator()(const std::string& lhs, int rhs);
        bool operator()(int lhs, const std::string& rhs);
         };
         ...
         std::vector<int> v;
    std::string k("abc");

    std::equal_range(v.begin(), v.end(), k, Compare());
Now this only works if there is *not* a constraint stating that the
value type of ForwardIterator == T.
Is the above well-defined in terms of the Standard?