#include <iosfwd.h>
aka2::isstream is a typedef name of std::istringstream.
For g++2.95, aka2::isstream is a std::istrstream-derived class, because std::istringstream does not work.
aka2::isstream declaration for g++2.95 is shown as below.
namespace aka2 { class isstream : public std::istrstream { public: isstream(const std::string &str); };