true if Frame 
still is a candidate for backtracking; false otherwise.<module>:<goal>. 
Do not instantiate variables in this goal unless you know what 
you are doing! Note that the returned term may contain references to the 
frame and should be discarded before the frame terminates.248The 
returned term is actually an illegal Prolog term that may hold 
references from the global to the local stack to preserve the variable 
names.The variant parent_goal(-Parent) unifies the frame 
reference of the parent of the found frame with Parent. That 
allows for finding frames higher up in the stack running the same goal.
goal, but only returning the [<module>:]<name>/<arity> 
term describing the term, not the actual arguments. It avoids creating 
an illegal term as goal and is used by the library library(prolog_stack).true if Frame 
is the top Prolog goal from a recursive call back from the foreign 
language; false otherwise.true if the frame is 
hidden from the user, either because a parent has the hide-childs 
attribute (all system predicates), or the system has no trace-me 
attribute.true if this frame was skipped in the 
debugger.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).
clause.
This predicate is used for the graphical debugger to show the choice point stack.
true if no choice point exists 
that is more recent than the entry of the clause in which it appears. 
There are few realistic situations for using this predicate. It is used 
by the
prolog/0 
top level to check whether Prolog should prompt the user for 
alternatives. Similar results can be achieved in a more portable fashion 
using call_cleanup/2.