Is the following supposed to compile: enum visitor_numerals { visitor_n0 , visitor_n1 }; typedef mpl::vector_c<visitor_numerals,visitor_n0> vec_viz_type; typedef mpl::at_c<vec_viz_type,0>::type vec_viz0_type; it does with intel but with gcc, I get: bjam --v2 toolset=gcc vector_enum_test ...patience... ...found 751 targets... ...updating 4 targets... gcc.compile.c++ ../../../../bin.v2/lje/libs/fields_visitor/test/vector_enum_test.test/gcc/debug/vector_enum_test.o /home/evansl/prog_dev/boost-release/boost_1_32_0/boost/mpl/aux_/preprocessed/gcc/vector_c.hpp: In instantiation of `boost::mpl::vector_c<visitor_numerals, 0l, 2147483647l, 2147483647l, 2147483647l, 2147483647l, 2147483647l, 2147483647l, 2147483647l, 2147483647l, 2147483647l, 2147483647l, 2147483647l, 2147483647l, 2147483647l, 2147483647l, 2147483647l, 2147483647l, 2147483647l, 2147483647l, 2147483647l>': /home/evansl/prog_dev/boost-release/boost_1_32_0/boost/mpl/aux_/has_tag.hpp:20: instantiated from `boost::mpl::aux::has_tag<test()::vec_viz_type, mpl_::bool_< false> >' /home/evansl/prog_dev/boost-release/boost_1_32_0/boost/mpl/sequence_tag.hpp:115: instantiated from `boost::mpl::sequence_tag<test()::vec_viz_type>' /home/evansl/prog_dev/boost-release/boost_1_32_0/boost/mpl/at.hpp:45: instantiated from `boost::mpl::at_c<test()::vec_viz_type, 0l>' vector_enum_test.cpp:11: instantiated from here /home/evansl/prog_dev/boost-release/boost_1_32_0/boost/mpl/aux_/preprocessed/gcc/vector_c.hpp:47: error: invalid conversion from `long int' to `visitor_numerals'