anchor.diff:               ,set))))))
   
   (mac in (x &rest choices)
  -  "Checks if the result of evaluating x is the result of
  -   one of the other arguments. Only evaluates arguments
  -   as necessary"
  +  "Returns t if X is one of the results of evaluating every CHOICE
  +   (lazily)."
     (w/uniq val
       `(let ,val ,x
          (or ,@(map (fn (c) `(is ,val ,c)) choices)))))
   
   (mac cart (f xs ys)
  -  "Applies the function f to a subset of the cartesian product of xs and 
  -   ys. The element from xs is bound to 'it' which can be used to change what
  -   ys is"
  +  "Applies F to a variation of the cartesian product of XS and YS.
  +   While going through XS, every element is bound to 'it' which
  +   can be used to modify YS."
     (w/uniq y
  -    `(mapcan (fn (it) ; we can use mapcan because map creates new conses
  +    `(mapcan (fn (it) ; It is okay to use mapcan since map conses.
                    (map (fn (,y)
                             (funcall ,f it ,y))
                         ,ys))
  
positive.code: ;;;; utilities which do not belong in any other file
  
  (in-package :clamp)
  
  (mac ado (&body body)
    "Evaluates each expression with it bound to the result of
     the previous one. Returns the value of the last expression"
    (if (null body)
          nil
        (single body)
  
negative.code:        ,set)))
  
  (mac or= (place new)
    "If PLACE is nil, assign the result of evaluating NEW there.
     Otherwise returns whatever value was already in PLACE and does not
     evaluate NEW."
    (mvb (vars forms var set access)
         (get-setf-expansion place)
      `(withs (,@(mappend #'list vars forms) ,(car var) (or ,access ,new))
         ,set)))
  
  (mac or2= (place new)
    "Equivalent to or= but will not carry through with the assignment 
     if accessing PLACE has a second return value which is non-nil."
    (mvb (vars forms var set access)
         (get-setf-expansion place)
      (w/uniq (val win)
  