E1:     C1 CALL pred builtin_call_rep.main/2-0 (det) builtin_call_rep.m:17
mdb> Contexts will not be printed.
mdb> mdb> mdb> echo on
Command echo enabled.
mdb> step
      E2:     C2 CALL func int.+/2-0 (det)
mdb> print proc_body
	proc_defn_rep([head_var_rep(1, var_mode_rep/2), head_var_rep(2, var_mode_rep/2), head_var_rep(3, var_mode_rep/2)], goal_rep(atomic_goal_rep("int.m", NN, [|]/2, builtin_call_rep/3), det_rep, unit), empty, no, det_rep)
mdb> browse proc_body
browser> cd 2
browser> ls
goal_rep(atomic_goal_rep("int.m", NN, [3], builtin_call_rep("int", "+", [1, 2, 3])), det_rep, unit)
browser> quit
mdb> f
      E3:     C2 EXIT func int.+/2-0 (det)
mdb> dd -d 3 -n 7
+(1, 2) = 3
Valid? b 3
browser> mark
Found incorrect contour:
+(1, 2) = 3
Is this a bug? y
      E3:     C2 EXIT func int.+/2-0 (det)
mdb> c
3