Compilare: user.cpp: In function ‘int prec(char)’: user.cpp:71:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (pos == string::npos) ^ user.cpp: In function ‘int main()’: user.cpp:83:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] FOR(i, 0, expr.size()) { ^ user.cpp:33:42: note: in definition of macro ‘FOR’ #define FOR(i, a, b) for (int i = a; i < b; ++i) ^ user.cpp: In function ‘int result(int, int, char)’: user.cpp:59:1: warning: control reaches end of non-void function [-Wreturn-type] } ^ user.cpp: In function ‘int main()’: user.cpp:82:6: warning: ‘num’ may be used uninitialized in this function [-Wmaybe-uninitialized] int num; ^