Compilare: user.cpp: In function ‘int calc(bool)’: user.cpp:38: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘int main()’: user.cpp:71: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:72: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp: In function ‘int eval(int, int, char)’: user.cpp:31: warning: control reaches end of non-void function