Compilare: user.cpp: In function ‘int put_first_two(int&, char*, std::stack<int>&, std::stack<char>&)’: user.cpp:31:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (i < strlen(foo) - 1) ^ user.cpp: In function ‘void eval_expr(char*)’: user.cpp:110:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (i < strlen(foo)) ^ user.cpp: In function ‘void deal_with_popping(std::stack<int>&, std::stack<char>&)’: user.cpp:48:13: warning: ‘result’ may be used uninitialized in this function [-Wmaybe-uninitialized] int result; ^ user.cpp: In function ‘void deal_with_brackets(std::stack<int>&, std::stack<char>&)’: user.cpp:73:13: warning: ‘result’ may be used uninitialized in this function [-Wmaybe-uninitialized] int result; ^