Unary predicate for shared_ptr == 'real' pointer?

This is probably more of a C++ than an boost question but, since it involves shared_ptr, I thought I'd try it here first. I've got a vector of shared_ptrS (e.g., vector v;) and I need to find the entry given the 'real' pointer to the underlying T. Looping thru the vector like this: <snippet> for( vectorget() == real_this){...} } </snippet> works but seems klunky. I should be able to use [find_if( v.begin(), v.end (), ???)] but I can't work out the predicate. Any help or "pointers" ;) will be greatly appreciated. TIA