foo.cc: In member function ‘bool Complex::operator>(const Complex&) const’:
foo.cc:42:30: error: ‘pow’ was not declared in this scope
   42 |                 double sq1 = pow(r, 2) + pow(i, 2);
      |                              ^~~
foo.cc:43:33: error: ‘sqrt’ was not declared in this scope
   43 |                 double sq1rt1 = sqrt(sq1);
      |                                 ^~~~