anchor.diff:                        (pdl-satisfies m w (third f))))))
   
   
  -; Now we verify the semantics of programs. First, we look at programs in
  -; "isolation" -- that is, separate from the concept of satisfiability of
  -; formulae:
  +
  +; Now we verify the semantics of programs.
   
   
   (defthm atomic-prog-value-is-correct
  
positive.code: 
  
  
  ; here
  
  
  ; we could perhaps declare this an equivalence relation....
  (defun seteq (A B)
    (and (subsetp A B) (subsetp B A)))
  
  ; define reachability. then b \in p*[i] iff b is reachable from p.
  
  
  (defthm star-prog-value-is-correct
    (implies (equal (len p) 2)
             
  
  
  ; Correctness of semantics of complex programs:
  
  ;here
  
  
negative.code: 
  (include-book "ordinals/lexicographic-ordering" :dir :system)
  
  (set-gag-mode :goals)
  
  
  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
  