Compilare: user.cpp: In function ‘void bring_to_standard_form(std::string&)’: user.cpp:8:18: warning: array subscript has type ‘char’ [-Wchar-subscripts] if(!buf[x]){ ^ user.cpp:9:18: warning: array subscript has type ‘char’ [-Wchar-subscripts] buf[x] = cur++; } ^ user.cpp:10:18: warning: array subscript has type ‘char’ [-Wchar-subscripts] x = buf[x]; } ^