# down 2;;
----------------------------------------
# # 
0 2 
....main....
[ext] H; x: A; J[x]  A
====
[ext] H; x: A  False; J[x]; v: False  C[x]

BY 

++++++++++
- : unit = ()
# refine dT 4;;
----------------------------------------
# * 
2 0 
....main....
[ext] H; x: A; J[x]  A
====
[ext] H; x: A  False; J[x]; v: False  C[x]

BY dT 4

++++++++++
- : unit = ()
# 