[Boost-users] [Proto] typeof in Hello World example

Dear all, I have recently started reading about Proto and am only crawling through the user guide. So, sorry if the question is too newbie... I see in the Hello World example at the Getting Started section http://boost.org/doc/libs/1_44_0/doc/html/proto/users_guide.html#boost_proto... in the Hello World example, the following header is also included: I was suspicious that this is not needed for this very example. So, I removed it and GCC 4.5.1 compiled it happily. I see also that this header is not included in the same example in the Example section of the user guide: http://boost.org/doc/libs/1_44_0/doc/html/proto/users_guide.html#boost_proto... Am I right in guessing that this header is not needed then? TIA, --Hossein