#define ORDER_PP_DEF_8h_longest ORDER_PP_FN( \
8fn(8M, 8P, \
    8if(8is_0(8M), \
        8P, \
        8let((8L, 8seq_size(8hailstone(8M))), \
             8h_longest(8dec(8M), \
                        8if(8greater(8L, 8tuple_at_1(8P)), \
                            8pair(8M, 8L), 8P))))) )

ORDER_PP(
  8let((8P, 8h_longest(8nat(1,0,0,0,0,0), 8pair(0, 0))),
       8pair(8to_lit(8tuple_at_0(8P)), 8to_lit(8tuple_at_1(8P))))
)