anchor.diff:  ;; last expression assigned to a gensym which will replace
   ;; it in the parent expression.
   (defun expex-body (ex x &optional (s '~%ret))
  +  (when (not x)	; Always return NIL.
  +	(setf x '((identity nil))))
     (with (e (expex-list ex x))
      	(expex-make-return-value ex e s)))
   
  
positive.code: 		(cons (car x) (expex-list ex (cdr x))))))
  
  (defun expex-make-return-value (ex e s)
    (with (b (butlast e)
  		 l (last e)
  		 la (car l))
     	(if (expex-returnable? ex la)
  		(append b (if (%setq? la)
  
negative.code: ;;;;; nix operating system project
  ;;;;; lisp compiler
  ;;;;; Copyright (c) 2006-2008 Sven Klose <pixel@copei.de>
  ;;;;; 
  ;;;;; Breaks up nested expressions into lists of assignments.
  