/in/foo.cc: In member function 'double Complex::modulus() const':
/in/foo.cc:15:16: error: 'sqrt' was not declared in this scope
   15 |         return sqrt(real * real + imag * imag);
      |                ^~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:37:5: error: 'sort' was not declared in this scope; did you mean 'short'?
   37 |     sort(complexes.begin(), complexes.end());
      |     ^~~~
      |     short