Compilare: user.cpp: In function ‘int main()’: user.cpp:30:12: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i<s.size()) ~^~~~~~~~~ user.cpp:43:43: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(ok==0 and issemn(s[i])==0 and i!=s.size()-1) ~^~~~~~~~~~~~ user.cpp:49:32: warning: array subscript has type ‘char’ [-Wchar-subscripts] coeficient[s[i]]+=nr; ^ user.cpp:58:32: warning: array subscript has type ‘char’ [-Wchar-subscripts] coeficient[s[i]]-=nr; ^ user.cpp:45:9: warning: ‘semn’ may be used uninitialized in this function [-Wmaybe-uninitialized] if(semn=='+') ^~