Compilare: user.cpp: In function ‘bool match(const number&, const number&)’: user.cpp:34: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘void add(number&, number)’: user.cpp:57: warning: comparison between signed and unsigned integer expressions user.cpp:60: warning: comparison between signed and unsigned integer expressions user.cpp:84: warning: comparison between signed and unsigned integer expressions