Hi! Here is an article that explains some of the issues involved in binary compatibility for C++ libraries: http://www-classic.be.com/aboutbe/benewsletter/Issue79.html#Insight I don't propose that we adopt their solution to the problem because as GiNaC is an open source project, it's easier for users to upgrade to a current GiNaC version. But it's nice to know which chanegs to GiNaC will break binary compatibility (and will require resetting the INTERFACE_AGE and BINARY_AGE variables in configure.in). Bye, Christian -- / Coding on PowerPC and proud of it \/ http://www.uni-mainz.de/~bauec002/