[Haskell-cafe] enumeration I/O and non-sequential access

Hello, I've recently been looking at Oleg's Iteratee approach to I/O (http://okmij.org/ftp/Haskell/Iteratee/), and I was wondering about something. In general this seems to be a very good approach to handling sequential access, but I don't see a means of applying it where non-sequential (esp. random) access is desired. In fact, the only way I see of doing so is to either hold references to all read data in memory until the file has finished processing, or to iterate over the file multiple times, depending on how the data is to be processed. I can't see how either of these approaches would scale well. Is this an actual problem? Is there already a solution that I'm not aware of? Thanks, John Lato