#t if obj is a calling stack.
Return the identifier given to stack by
Return the length of stack.
Return the index’th frame from stack.
Display a backtrace to the output port port. stack
is the stack to take the backtrace from, first specifies
where in the stack to start and depth how many frames
to display. first and depth can be
which means that default values will be used.
If highlights is given it should be a list; the elements
of this list will be highlighted wherever they appear in the