RosettaCodeData/Task/Doubly-linked-list-Element-insertion/Pascal/doubly-linked-list-element-insertion-1.pas

procedure insert_link( a, b, c: link_ptr );
begin
  a^.next := c;
  if b <> nil then b^.prev := c;
  c^.next := b;
  c^.prev := a;
end;