Compilare: user.cpp: In function 'int tr(int)': user.cpp:16: warning: NULL used in arithmetic user.cpp:20: warning: the address of 'p' will always evaluate as 'true' user.cpp:21: warning: the address of 'p' will always evaluate as 'true' user.cpp:22: warning: the address of 'p' will always evaluate as 'true' user.cpp:24: warning: the address of 'p' will always evaluate as 'true' user.cpp:25: warning: the address of 'p' will always evaluate as 'true' user.cpp:28: warning: the address of 'p' will always evaluate as 'true' user.cpp:29: warning: the address of 'p' will always evaluate as 'true' user.cpp:30: warning: the address of 'p' will always evaluate as 'true' user.cpp:32: warning: comparison between signed and unsigned integer expressions