Compilare: main.cpp: In member function 'BigInt& BigInt::operator+=(BigInt)': main.cpp:19:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 19 | for (int i = 0; i < termen.digits.size(); i++) { | ~~^~~~~~~~~~~~~~~~~~~~~~ main.cpp: In member function 'BigInt& BigInt::operator-=(BigInt)': main.cpp:33:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 33 | for (int i = 0; i < termen.digits.size(); i++) { | ~~^~~~~~~~~~~~~~~~~~~~~~