/in/foo.cc: In member function 'BigInt BigInt::add(const BigInt&) const':
/in/foo.cc:64:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   64 |             for (int i=0;i<num1.length()||i<num2.length()||carry;++i) {
      |                          ~^~~~~~~~~~~~~~
/in/foo.cc:64:44: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   64 |             for (int i=0;i<num1.length()||i<num2.length()||carry;++i) {
      |                                           ~^~~~~~~~~~~~~~
/in/foo.cc:65:30: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   65 |                 int digit1=(i<num1.length())?num1[i]-'0':0;
      |                             ~^~~~~~~~~~~~~~
/in/foo.cc:66:30: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   66 |                 int digit2=(i<num2.length())?num2[i]-'0':0;
      |                             ~^~~~~~~~~~~~~~
/in/foo.cc:78:30: error: request for member 'add' in '(const BigInt*)this', which is of pointer type 'const BigInt*' (maybe you meant to use '->' ?)
   78 |                 return *this.add(BigInt("-"+other.num));
      |                              ^~~