1:      1  1 CALL pred pd.main/2-0 (det) pd.m:14
mdb> echo on
Command echo enabled.
mdb> register --quiet
mdb> break rev
 0: + stop  interface func pd.rev/1-0 (det)
mdb> continue
       2:      2  2 CALL func pd.rev/1-0 (det) pd.m:19 (pd.m:15)
mdb> finish
      15:      2  2 EXIT func pd.rev/1-0 (det) pd.m:19 (pd.m:15)
mdb> dd -d 3 -n 7
rev([1, 2, 3]) = []
Valid? no
rev_2([1, 2, 3], []) = []
Valid? pd
      14:      3  3 EXIT func pd.rev_2/2-0 (det) pd.m:23 (pd.m:19)
mdb> retry
       3:      3  3 CALL func pd.rev_2/2-0 (det) pd.m:23 (pd.m:19)
mdb> step
       4:      3  3 SWTC func pd.rev_2/2-0 (det) s2-2; pd.m:24
mdb> step
       5:      4  4 CALL func pd.rev_2/2-0 (det) pd.m:23 (pd.m:24)
mdb> finish
      13:      4  4 EXIT func pd.rev_2/2-0 (det) pd.m:23 (pd.m:24)
mdb> dd -d 3 -n 7
rev_2([2, 3], [1]) = []
Valid? no
rev_2([3], [2, 1]) = []
Valid? pd
      12:      5  5 EXIT func pd.rev_2/2-0 (det) pd.m:23 (pd.m:24)
mdb> dd -d 3 -n 7
rev_2([3], [2, 1]) = []
Valid? no
rev_2([], [3, 2, 1]) = []
Valid? no
Found incorrect contour:
rev_2([], [3, 2, 1]) = []
Is this a bug? yes
      11:      6  6 EXIT func pd.rev_2/2-0 (det) pd.m:23 (pd.m:24)
mdb> quit -y