/in/ex4.cpp: In member function 'virtual int bookInventory::searchBook(const string&) const':
/in/ex4.cpp:18:18: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
     for(int i=0;i<numBooks;i++){
                 ~^~~~~~~~~
/in/ex4.cpp: In member function 'virtual void bookInventory::removeBook(int)':
/in/ex4.cpp:44:19: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
     if(ID>=1 && ID<=numBooks){
                 ~~^~~~~~~~~~
/in/ex4.cpp:45:23: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
         for(int i=ID;i<numBooks;i++){
                      ~^~~~~~~~~
/in/ex4.cpp: In member function 'virtual void bookInventory::printInventory() const':
/in/ex4.cpp:56:22: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
         for(int i=0;i<numBooks;i++){
                     ~^~~~~~~~~
/in/ex4.cpp: In member function 'void library::borrowBook(int)':
/in/ex4.cpp:71:19: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
     if(ID>=1 && ID<=numBooks){
                 ~~^~~~~~~~~~
/in/ex4.cpp: In member function 'void library::returnBook(int)':
/in/ex4.cpp:84:19: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
     if(ID>=1 && ID<=numBooks){
                 ~~^~~~~~~~~~
/in/ex4.cpp: In member function 'void library::listBorrowed() const':
/in/ex4.cpp:98:18: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
     for(int i=0;i<numBooks;i++){
                 ~^~~~~~~~~
cc1plus: all warnings being treated as errors
/in/compile/Makefile:26: recipe for target 'ex4.o' failed
make: *** [ex4.o] Error 1