Compiling this: #include #include #include <vector> #include <cstdlib> #include #include <iostream> using std::ostream; class Value { public: explicit Value(int amount) : m_amount(amount) {} void WriteTo(ostream& stream) const { stream << m_amount; } private: int m_amount; }; ostream& operator <<(ostream& stream, const Value& value) { value.WriteTo(stream); return stream; } int main() { typedef boost::shared_ptr<Value> ValuePtr; std::vector<ValuePtr> valueBuffer; for(int count = 0; 10 > count; ++count){ valueBuffer.push_back(ValuePtr(new Value(::rand()))); } BOOST_FOREACH(ValuePtr value, valueBuffer){ std::cout << *value << std::endl; } return 0; } on Fedora 10 (Intel) produces error output like: /usr/include/boost/foreach.hpp:223: error: expected nested-name-specifier before ‘int’ /usr/include/boost/foreach.hpp:223: error: two or more data types in declaration of ‘parameter’ /usr/include/boost/foreach.hpp:224: error: default template arguments may not be used in function templates Value.cpp: In function ‘int main()’: Value.cpp:34: error: no matching function for call to ‘not_(boost::is_array > >*)’ Value.cpp:34: error: no matching function for call to ‘not_(boost::foreach::is_noncopyable > >*)’ Value.cpp:34: error: no matching function for call to ‘not_(boost::is_array > >*)’ Value.cpp:34: error: no matching function for call to ‘not_(boost::foreach::is_noncopyable > >*)’ Value.cpp:34: error: no matching function for call to ‘not_(boost::is_array > >*)’ Value.cpp:34: error: no matching function for call to ‘not_(boost::foreach::is_noncopyable > >*)’ If the first included header file is removed from the code, it builds successfully. Even though the code in this example doesn't technically need that first header file included, it is representative of code that does. What is needed so this code can build successfully while including all the header files?