Hi all, I have been using boost's variant library in a project, and I've noticed that when I import the class using the variant class into other classes I start having the strangest compilation problems. I've been dealing with these problems for the last few months by isolating that code as much as possible. I've put it behind a factory which returns an abstract class which hides the fact that a variant is being used by the implementing class at all. This keeps other classes from having to import the implementing class and by extension the boost variant header, but it also makes it difficult to make full use of visitors together with the variant because creating new visitors that include the implementing class leads to these same strange compilation problems. I was hoping that someone might be able to give me a better diagnosis for the underlying reason for these problems. I've included the error output below. If anyone can give me any greater insight into what's causing these errors, I would be extremely grateful. Best, Greg 1>C:\Program Files (x86)\boost\boost_1_42\boost/mpl/aux_/integral_wrapper.hpp(80): error C2544: expected ')' for operator '()' 1> C:\Program Files (x86)\boost\boost_1_42\boost/mpl/aux_/integral_wrapper.hpp(81) : see reference to class template instantiation 'boost::mpl::integral_c<T,N>' being compiled 1>C:\Program Files (x86)\boost\boost_1_42\boost/mpl/aux_/integral_wrapper.hpp(80): error C2146: syntax error : missing ';' before identifier 'L' 1>C:\Program Files (x86)\boost\boost_1_42\boost/mpl/aux_/integral_wrapper.hpp(80): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int 1>C:\Program Files (x86)\boost\boost_1_42\boost/mpl/aux_/integral_wrapper.hpp(80): error C2059: syntax error : ')' 1>C:\Program Files (x86)\boost\boost_1_42\boost/mpl/aux_/integral_wrapper.hpp(80): error C2143: syntax error : missing ';' before 'const' 1>C:\Program Files (x86)\boost\boost_1_42\boost/mpl/aux_/integral_wrapper.hpp(80): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int 1>C:\Program Files (x86)\boost\boost_1_42\boost/mpl/aux_/integral_wrapper.hpp(80): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int 1>C:\Program Files (x86)\boost\boost_1_42\boost/mpl/aux_/integral_wrapper.hpp(80): error C2059: syntax error : '{' 1>C:\Program Files (x86)\boost\boost_1_42\boost/mpl/aux_/integral_wrapper.hpp(80): error C2334: unexpected token(s) preceding '{'; skipping apparent function body 1>C:\Program Files (x86)\boost\boost_1_42\boost/mpl/aux_/integral_wrapper.hpp(80): error C2544: expected ')' for operator '()' 1> C:\Program Files (x86)\boost\boost_1_42\boost/type_traits/integral_constant.hpp(21) : see reference to class template instantiation 'boost::mpl::integral_c<T,N>' being compiled 1> with 1> [ 1> T=size_t, 1> N=0 1> ] 1> C:\Program Files (x86)\boost\boost_1_42\boost/type_traits/alignment_of.hpp(109) : see reference to class template instantiation 'boost::integral_constant<T,val>' being compiled 1> with 1> [ 1> T=size_t, 1> val=0 1> ] 1>C:\Program Files (x86)\boost\boost_1_42\boost/mpl/aux_/integral_wrapper.hpp(80): error C2146: syntax error : missing ';' before identifier 'L' 1>C:\Program Files (x86)\boost\boost_1_42\boost/mpl/aux_/integral_wrapper.hpp(80): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int 1>C:\Program Files (x86)\boost\boost_1_42\boost/mpl/aux_/integral_wrapper.hpp(80): error C2059: syntax error : ')' 1>C:\Program Files (x86)\boost\boost_1_42\boost/mpl/aux_/integral_wrapper.hpp(80): error C2143: syntax error : missing ';' before 'const' 1>C:\Program Files (x86)\boost\boost_1_42\boost/mpl/aux_/integral_wrapper.hpp(80): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int 1>C:\Program Files (x86)\boost\boost_1_42\boost/mpl/aux_/integral_wrapper.hpp(80): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int 1>C:\Program Files (x86)\boost\boost_1_42\boost/mpl/aux_/integral_wrapper.hpp(80): error C2059: syntax error : '{' 1>C:\Program Files (x86)\boost\boost_1_42\boost/mpl/aux_/integral_wrapper.hpp(80): error C2334: unexpected token(s) preceding '{'; skipping apparent function body 1>C:\Program Files (x86)\boost\boost_1_42\boost/mpl/aux_/integral_wrapper.hpp(80): error C2544: expected ')' for operator '()' 1> C:\Program Files (x86)\boost\boost_1_42\boost/type_traits/integral_constant.hpp(21) : see reference to class template instantiation 'boost::mpl::integral_c<T,N>' being compiled 1> with 1> [ 1> T=size_t, 1> N=8 1> ] 1> C:\Program Files (x86)\boost\boost_1_42\boost/type_traits/alignment_of.hpp(89) : see reference to class template instantiation 'boost::integral_constant<T,val>' being compiled 1> with 1> [ 1> T=size_t, 1> val=8 1> ] 1> C:\Program Files (x86)\boost\boost_1_42\boost/type_traits/type_with_alignment.hpp(289) : see reference to class template instantiation 'boost::alignment_of<T>' being compiled 1> with 1> [ 1> T=boost::detail::max_align 1> ]