E1:     C1 CALL pred io_tab_impure.main/2-0 (det) io_tab_impure.m:15
mdb> mdb> echo on
Command echo enabled.
mdb> table_io allow
mdb> table_io start
I/O tabling started.
mdb> break impure_print_hello
 0: + stop  interface pred io_tab_impure.impure_print_hello/0-0 (det)
mdb> c
      E2:     C2 CALL pred io_tab_impure.impure_print_hello/0-0 (det) io_tab_impure.m:28 (io_tab_impure.m:24)
mdb> f
hello      E3:     C2 EXIT pred io_tab_impure.impure_print_hello/0-0 (det) io_tab_impure.m:28 (io_tab_impure.m:24)
mdb> dd -a
impure_print_hello
1 tabled IO action:
print("hello")
Valid? n
impure_print("hello")
1 tabled IO action:
print("hello")
Valid? n
make_io_state(_)
Valid? y
print("hello", _, _)
1 tabled IO action:
print("hello")
Valid? n
Found incorrect contour:
print("hello", _, _)
1 tabled IO action:
print("hello")
Is this a bug? y
      E4:     C3 EXIT pred io_tab_impure.print/3-0 (det) io_tab_impure.m:40 (io_tab_impure.m:35)
mdb> quit -y