I've just uploaded proto v3 to the file vault (http://www.boost-consulting.com/vault/index.php?directory=Template%20Metapro...). Proto is a toolkit for implementing domain-specific embedded languages in C++ using expression templates. The new version has a completely rewritten set of transforms that are incompatible with the old transforms, so this is a breaking change. You can read all about the new transforms here: http://boost-sandbox.sourceforge.net/libs/proto/doc/html/boost_proto/users_g... The short story is that transforms are now simply TR1-style function objects, and they can be composed using function types (the so-called "round lambda" syntax), making expression tree transformations readable and concise. -- Eric Niebler Boost Consulting www.boost-consulting.com