true if Frame 
still is a candidate for backtracking. false otherwise.user 
the goal is represented as <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.88The 
returned term is actually an illegal Prolog term that may hold 
references from the global- to the local stack to preserve the variable 
names.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.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.
true if no choicepoint exists 
that is more recent than the entry of the clause in which is appears. 
There are few realistic situations for using this predicate. It is used 
by the
prolog/0 
toplevel to check whether Prolog should prompt the user for 
alternatives. Similar results can be achieved in a more portable fashion 
using call_cleanup/2.