Compilare: main.cpp: In function 'int main()': main.cpp:27:14: warning: ignoring return value of 'constexpr decltype (__cont.empty()) std::empty(const _Container&) [with _Container = stack<char>; decltype (__cont.empty()) = bool]', declared with attribute 'nodiscard' [-Wunused-result] 27 | empty(s_aux); | ~~~~~^~~~~~~ In file included from /usr/include/c++/12.2.1/string:52, from /usr/include/c++/12.2.1/bits/locale_classes.h:40, from /usr/include/c++/12.2.1/bits/ios_base.h:41, from /usr/include/c++/12.2.1/ios:42, from /usr/include/c++/12.2.1/ostream:38, from /usr/include/c++/12.2.1/iostream:39, from main.cpp:1: /usr/include/c++/12.2.1/bits/range_access.h:283:5: note: declared here 283 | empty(const _Container& __cont) noexcept(noexcept(__cont.empty())) | ^~~~~ main.cpp:40:21: warning: suggest explicit braces to avoid ambiguous 'else' [-Wdangling-else] 40 | else if (s_aux.size()) | ^