Compilare: user.c: In function 'prefix': user.c:14: warning: suggest parentheses around assignment used as truth value user.c: In function 'main': user.c:27: warning: implicit declaration of function 'strlen' user.c:27: warning: incompatible implicit declaration of built-in function 'strlen' /tmp/ccELqrYW.o: In function `main': user.c:(.text+0xd9): warning: the `gets' function is dangerous and should not be used.