- Requests a reference to the first older choice point.
- Requests a reference to the frame to which the choice point refers.
- Requests the type. Defined values are
clause(the goal has alternative clauses),
foreign(non-deterministic foreign predicate),
jump(clause internal choice point),
top(first dummy choice point),
catch(catch/3 to allow for undo),
debug(help the debugger), or
none(has been deleted).
This predicate is used for the graphical debugger to show the choice point stack.