Compilare: user.cpp: In function ‘bool is_alpha(char)’: user.cpp:7: warning: suggest parentheses around ‘&&’ within ‘||’ user.cpp: In function ‘int main()’: user.cpp:12: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:13: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result