The Boost.Typeof library does a lot of work to determine the type of an expression. At last week's meeting, the C++ committee voted to add "decltype" into the C++0x standard. decltype is what we want from typeof: a proper, reference-preserving way to get the type of an arbitrary expression. As of today, GCC 4.3's experimental C++0x mode contains support for decltype. I have updated the Boost Config library (on the CVS trunk) to contain BOOST_HAS_DECLTYPE, indicating the presence of decltype. A sufficiently-motivated person could certainly use this macro to give a simple implementation of decltype for C++0x compilers... There is nightly testing of Boost's trunk on the latest version of GCC 4.3 (also built nightly), so we will get appropriate testing of C+ +0x features throughout Boost. - Doug