The attached sample fails in IBM VisualAge C++ V6.0 for AIX with the following message: vacpp.compile.c++ bin/vacpp/debug/seq.o "seq.cpp", line 10.14: 1540-0861 (S) Too few arguments are specified for macro "BOOST_PP_IIF_0". Empty arguments are used. "/home/tk/ext_projects/boost_life/boost/boost/preprocessor/control/iif.h pp", line 31.10: 1540-0425 (I) "BOOST_PP_IIF_0" is defined on line 31 of "seq.cpp". "seq.cpp", line 10.14: 1540-0861 (S) Too few arguments are specified for macro "BOOST_PP_IIF_0". Empty arguments are used. "/home/tk/ext_projects/boost_life/boost/boost/preprocessor/control/iif.h pp", line 31.10: 1540-0425 (I) "BOOST_PP_IIF_0" is defined on line 31 of "seq.cpp". Any PP guru knows how to fix this? For motivation, this problem is currently breaking a good portion of Boost.Test in vacpp, and transitively lots of test cases in other libraries. Thank you, Joaquín M López Muñoz Telefónica, Investigación y Desarrollo