Compilare: user.cpp: In function ‘int digit(int&)’: user.cpp:44:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( ;i<s.size() && isdigit(s[i]);i++) nr=nr*10+s[i]-'0'; ^ user.cpp: In function ‘void rezolvare()’: user.cpp:51:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<s.size();i++) ^ user.cpp:72:56: warning: array subscript has type ‘char’ [-Wchar-subscripts] while(op.empty()==0 && val[op.top()]>=val[s[i]]) evaluare(); ^ user.cpp:72:67: warning: array subscript has type ‘char’ [-Wchar-subscripts] while(op.empty()==0 && val[op.top()]>=val[s[i]]) evaluare(); ^