Compilare: user.cpp: In function 'int eval2(std::string)': user.cpp:13: warning: comparison between signed and unsigned integer expressions user.cpp:28: warning: comparison between signed and unsigned integer expressions user.cpp: In function 'int eval(std::string)': user.cpp:41: warning: comparison between signed and unsigned integer expressions user.cpp:44: warning: comparison between signed and unsigned integer expressions user.cpp:52: warning: comparison between signed and unsigned integer expressions user.cpp:39: warning: unused variable 'ret' user.cpp: In function 'int main()': user.cpp:81: warning: comparison between signed and unsigned integer expressions user.cpp:90: warning: comparison between signed and unsigned integer expressions /tmp/cckB7aBk.o: In function `main': user.cpp:(.text+0x108b): warning: the `gets' function is dangerous and should not be used.