/in/foo.cc: In member function 'BigInt BigInt::add(const BigInt&) const':
/in/foo.cc:70:31: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   70 |             for (int i = 0; i < num1.length() || i < num2.length() || carry; ++i) {
      |                             ~~^~~~~~~~~~~~~~~
/in/foo.cc:70:52: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   70 |             for (int i = 0; i < num1.length() || i < num2.length() || carry; ++i) {
      |                                                  ~~^~~~~~~~~~~~~~~
/in/foo.cc:71:33: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   71 |                 int digit1 = (i < num1.length()) ? num1[i] - '0' : 0;
      |                               ~~^~~~~~~~~~~~~~~
/in/foo.cc:72:33: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   72 |                 int digit2 = (i < num2.length()) ? num2[i] - '0' : 0;
      |                               ~~^~~~~~~~~~~~~~~
/in/foo.cc:90:35: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   90 |                 for (int i = 0; i < num1.length(); ++i) {
      |                                 ~~^~~~~~~~~~~~~~~
/in/foo.cc:92:37: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   92 |                     int digit2 = (i < num2.length()) ? num2[i] - '0' : 0;
      |                                   ~~^~~~~~~~~~~~~~~