Compilare: user.cpp: In function ‘bool get_and(std::string)’: user.cpp:51:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i<s.size() && s[i]=='&') ^ user.cpp: In function ‘bool get_xor(std::string)’: user.cpp:61:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i<s.size() && s[i]=='^') ^ user.cpp: In function ‘bool eval(std::string)’: user.cpp:71:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i<s.size() && s[i]=='|') ^ user.cpp: In function ‘int main()’: user.cpp:87:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<s1.size();++i) ^ user.cpp:96:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<s2.size();++i){ ^