Compilare: main.cpp: In function 'i64 do_add(int*)': main.cpp:32:17: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 32 | while (*idx < expr.size() && (expr[*idx] == '+' || expr[*idx] == '-')) { | ~~~~~^~~~~~~~~~~~~ main.cpp: In function 'i64 do_multiply(int*)': main.cpp:48:17: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 48 | while (*idx < expr.size() && (expr[*idx] == '*' || expr[*idx] == '/')) { | ~~~~~^~~~~~~~~~~~~ main.cpp: In function 'i64 do_term(int*)': main.cpp:69:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 69 | while (*idx < expr.size() && expr[*idx] >= '0' && expr[*idx] <= '9') { | ~~~~~^~~~~~~~~~~~~