Compilare: user.cpp: In function ‘bool log(std::string)’: user.cpp:31:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0; i<s.size(); i++) ^ user.cpp:47:67: warning: array subscript has type ‘char’ [-Wchar-subscripts] if(st.size()==0 || st.top()=='(' || o[st.top()]<o[s[i]]) ^ user.cpp:51:75: warning: array subscript has type ‘char’ [-Wchar-subscripts] while(st.size()!=0 && st.top()!='(' && o[st.top()]>=o[s[i]]) ^ user.cpp: In function ‘int main()’: user.cpp:144:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (l<s1.size()) ^ user.cpp:152:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (l<s2.size()) ^