7 ; deconstruct our sofar-pair
8 sofar (\might_be_equal right_tail.
11 (and (and might_be_equal (not (isempty right_tail))) (eq? hd (head right_tail)))
15 ; we pass along the fold a pair
16 ; (might_for_all_i_know_still_be_equal?, tail_of_reversed_right)
17 ; when left is empty, the lists are equal if right is empty
19 true ; for all we know so far, they might still be equal
22 ; when fold is finished, check sofar-pair
23 (\might_be_equal right_tail. and might_be_equal (isempty right_tail))