/in/foo.cc: In member function 'SeqList SeqList::intersection(const SeqList&)':
/in/foo.cc:49:31: error: passing 'const SeqList' as 'this' argument discards qualifiers [-fpermissive]
   49 |             if (other.contains(data[i])) {
      |                 ~~~~~~~~~~~~~~^~~~~~~~~
/in/foo.cc:37:10: note:   in call to 'bool SeqList::contains(int)'
   37 |     bool contains(int value) {
      |          ^~~~~~~~