Compilare: main.cpp: In function 'long long int expr_fact()': main.cpp:43:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 43 | while(idx < s.size() && isdigit(s[idx])) { | ~~~~^~~~~~~~~~ main.cpp: In function 'long long int expr_pow()': main.cpp:52:12: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 52 | if(idx < s.size() && s[idx] == '^') { | ~~~~^~~~~~~~~~ main.cpp: In function 'long long int expr_div()': main.cpp:62:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 62 | while(idx < s.size() && s[idx] == '/') { | ~~~~^~~~~~~~~~ main.cpp: In function 'long long int expr_add()': main.cpp:72:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 72 | while(idx < s.size() && s[idx] == '+') { | ~~~~^~~~~~~~~~