[boost] iterator/transform_iterator.hpp has more dependencies than it needs?

My work likes to keep a minimal subset of boost in the project tree. One of the libraries we are using (I can't remember which off hand) requires transform_iterator.hpp which includes boost/function.hpp. I noticed when merging in the latest RC updates that I had commented out this header as it doesn't appear to be necessary and saves me from bringing yet another library into the mini-boost folder. Is this dependency actually necessary? Thanks, Michael Marcin