Compilare: user.cpp: In function ‘int main()’: user.cpp:32:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < s.size(); i++) ^ user.cpp:40:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < s.size(); i++) ^ user.cpp:53:82: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(s[j]!='='&&s[j]!='+'&&s[j]!='-'&&s[j]!='x'&&j < s.size()) ^ user.cpp:143:71: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(s[j]!='+'&&s[j]!='-'&&s[j]!='x'&&j < s.size()) ^ user.cpp:207:41: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] else if(j == s.size()) ^