Compilare: user.cpp: In function ‘bool eval()’: user.cpp:52: warning: array subscript has type ‘char’ user.cpp: In function ‘int main()’: user.cpp:106: warning: array subscript has type ‘char’ user.cpp:106: warning: array subscript has type ‘char’ user.cpp: In function ‘bool eval()’: user.cpp:39: warning: ‘r’ may be used uninitialized in this function