E1:     C1 CALL pred polymorphic_output.main/2-0 (det) polymorphic_output.m:20
mdb> echo on
Command echo enabled.
mdb> register --quiet
mdb> context none
Contexts will not be printed.
mdb> b functor_names
 0: + stop  interface func polymorphic_output.functor_names/1-0 (det)
mdb> c
      E2:     C2 CALL func polymorphic_output.functor_names/1-0 (det)
mdb> delete 0
 0: E stop  interface func polymorphic_output.functor_names/1-0 (det)
mdb> p goal
functor_names(two("three", 3, three("four", 4, "one", 1, empty, empty, empty), two("two", 2, empty, empty))) = _
mdb> format verbose
mdb> format_param lines 100
mdb> p goal
functor_names
1-two
| 1-"three"
| 2-3
| 3-three
| | 1-"four"
| | 2-4
| | 3-"one"
| | 4-1
| | 5-empty
| | 6-empty
| | 7-empty
| 4-two
|   1-"two"
|   2-2
|   3-empty
|   4-empty
2-_

mdb> format flat
mdb> browse goal
browser> ^1
browser> p
two("three", 3, three("four", 4, "one", 1, empty, empty, empty), two("two", 2, empty, empty))
browser> ^..^2
browser> p
'_'
browser> ^..^3
error: there is no subterm 3
browser> p
'_'
browser> ^..^r
browser> p
'_'
browser> quit
mdb> b std_util__det_arg
 0: + stop  interface func std_util.det_arg/2-0 (det)
mdb> c
      E3:     C3 CALL func std_util.det_arg/2-0 (det)
mdb> P
       Type (arg 1)           	two("three", 3, three("four", 4, "one", 1, empty, empty, empty), two/4)
       Index (arg 2)          	3
mdb> f
      E4:     C3 EXCP func std_util.det_arg/2-0 (det)
mdb> P
       Type (arg 1)           	two("three", 3, three("four", 4, "one", 1, empty, empty, empty), two/4)
       Index (arg 2)          	3
       Argument0              	two("two", 2, empty, empty)
mdb> c
Uncaught Mercury exception:
Software Error: det_arg: argument has wrong type
Last trace event was event #E5.
Last trace event before the unhandled exception was event #E6.