Compilare: user.cpp: In function ‘int main()’: user.cpp:14:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<s.size();i++) ^ user.cpp:41:14: warning: ‘prec’ may be used uninitialized in this function [-Wmaybe-uninitialized] {if(prec==')') ^