Compilare: user.cpp: In function 'int tr(int)': user.cpp:17: warning: NULL used in arithmetic 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:23: 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:26: 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:31: warning: the address of 'p' will always evaluate as 'true' user.cpp:33: warning: comparison between signed and unsigned integer expressions