Compilare: user.cpp: In function ‘void read_eval()’: user.cpp:29:26: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &n, &m); ^ user.cpp:33:36: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%s%d%d", op, &a, &b); ^ user.cpp:45:38: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &c, &d); ^ user.cpp: In function ‘int main()’: user.cpp:116:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("perspic.in", "rt", stdin); ^ user.cpp:117:41: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("perspic.out", "wt", stdout); ^