/in/foo.cc: In constructor 'SeqList::SeqList()':
/in/foo.cc:14:10: warning: converting to non-pointer type 'int' from NULL [-Wconversion-null]
    sl[k]=NULL;
          ^~~~
/in/foo.cc: In member function 'SeqList SeqList::Insert(SeqList)':
/in/foo.cc:27:12: warning: converting to non-pointer type 'int' from NULL [-Wconversion-null]
    t.sl[k]=NULL;
            ^~~~