CL-USER> (pxref:xref-file "/home/death/lisp/snippets/24-puzzle.lisp")
Cross-referencing file /home/death/lisp/snippets/24-puzzle.lisp.
......
6 forms processed.
; No value
CL-USER> (pxref:print-caller-trees)
Rooted calling trees:
  24-PUZZLE
     DFS
     MAKE-24-STATE
     24-STATE-NUMS
     24-EVAL
        24-EVAL
     24-STATE-EXPR
     :UNNAMED-LAMBDA

Cyclic calling trees:
  REC
     GOALP
     DFS
     REC
     SUCCESSORS
  NEW-STATE
     MAKE-24-STATE
     24-STATE-NUMS
     24-STATE-EXPR
     NEW-STATE
     :UNNAMED-LAMBDA
NIL