/home/tim/workspace/boost-trunk/boost/parameter/name.hpp:52:1: error: template argument 2 is invalid Note this is the first error, and that's unrelated to enable_if.
not quite: the second template argument which gcc complains about is an enable_if ...
/home/tim/workspace/boost-trunk/boost/fusion/iterator/equal_to.hpp:77:9: error: expected nested-name-specifier before ‘enable_if’ This message says a declaration of enable_if is missing. Either it's not properly qualified, or equal_to.hpp is not including it and was relying on other files to include it, which of course is very fragile. (missing includes is a very common bug in many Boost libraries though)
ok, there are some references to en/disable_if, which do not use the full namespace. i've submitted two patches to parameter and fusion [1,2], but there are possibly more issues. tim [1] https://svn.boost.org/trac/boost/ticket/6214 [2] https://svn.boost.org/trac/boost/ticket/6215