Hi again, pqs-1-00-03-boosted is available on the files section: http://groups.yahoo.com/group/boost/files/pqs/pqs-1-00-03-boost.ZIP This version is designed for inclusion in the boost library tree. and uses the namespace boost::pqs, where previous versions used physical-quantities. Tested on VC7.1 and gcc3.2. Currently I am working on complex physical-quantities which require a large number of operator overloads, and cant be achieved without violating the standard. 26.2.6.(See the q_complex.cpp and complex_example.cpp in examples for details of whats done so far in complex area.) Does pqs use mpl? Some but not much. I have had difficulties using mpl in this context. Which is basically to construct the return types of operators. I have found that this type of thing does the job in a scaleable manner: binary_operation<A,Op,B>. This computes a type and has a solitary result_type member which can be used with result_of. It also scales rather well and has come in very useful for complex physical-quanity definitions as well as my abstract_pq type. (see boost/pqs/class_template/abstract_identity/abstract_pq/abstract_pq.hpp in the distro for example of economies gained by this approach). Defining binary_operation<A,Op,B> for two types also automatically enables use of the binary_operator functors.(See boost/pqs/operators/binary_operators.hpp in the distro for details on this.) Major changes based on boost feedback 1) The namespace in this version has changed from physical_quantities to boost::pqs. 2) A tag mechanism has been added to distinguish (say) torque from energy. This works simply at the output level. See examples/torque_from_energy.cpp for more details. I still do not consider the library to be stable yet.(There may be a need for yet another tag in the units) I dont have any tests included, and the docs need a lot of work. At the moment it is still just for fun. regards Andy little