Compilare: user.cpp: In function ‘int main()’: user.cpp:30:41: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(s[j]==' ' && j<s.size())++j; ^ user.cpp:32:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(j<s.size()) ^ user.cpp:35:58: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(s[j]>='0' && s[j]<='9' && j<s.size()) ^ user.cpp:48:41: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(s[j]==' ' && j<s.size())++j; ^ user.cpp:50:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(j<s.size()) ^ user.cpp:53:58: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(s[j]>='0' && s[j]<='9' && j<s.size()) ^ user.cpp:58:43: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(s[j]=='+' || j==s.size()) ^ user.cpp:66:62: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(s[j]>='0' && s[j]<='9' && j<s.size()) ^