anchor.diff:         ((A 1) (if-true 'nil (if (equal (car '()) '?) 't  (memb? (cdr '())))))
          ((A) (equal-same 'nil))
          ((E A 1 1) (remb xs))
  -
          ((E A 1 1)
           (if-nest-E (atom xs)
             '()
  
positive.code:        (() (if-same (atom x) 't)))
        ((dethm ctx?/sub (x y)
           (if (ctx? x) (if (ctx? y) (equal (ctx? (sub x y)) 't) 't) 't))
  
         (star-induction y)
         (()
          (if-same (ctx? x)
  
negative.code:         (if-nest-A (set? (add-atoms (cdr a) bs))
            (equal (set? (add-atoms (car a) (add-atoms (cdr a) bs))) 't)
            't))
         ((E A E Q)
          (if-nest-E (set? (add-atoms (cdr a) bs))
            (equal (set? (add-atoms (car a) (add-atoms (cdr a) bs))) 't)
  