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:        ,set)))
  
  (mac or= (place new)
    "If the var is nil, it assigns the new value to it.
     Otherwise does nothing"
    (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)
    "Or= but also works on places that may be nil but return multiple
     values instead."
    (mvb (vars forms var set access)
         (get-setf-expansion place)
      (w/uniq (val win)
  
negative.code: ;;;; Utilities which do not belong in any other file.
  
  (in-package :clamp)
  
  (mac ado (&body body)
    "Evaluates each expression with the symbol 'it' bound to the result
     of the previous one. Returns the value of the last expression."
    (if (null body)
          nil
        (single body)
  