anchor.diff:           (macro-expand (expander expr))
            (map macro-expand expr))))))))
   
  +;;; QUASIQUOTE
   (defmacro (quasiquote x)
     (if (pair? x)
         (if (eq? (car x) 'unquote)
  
positive.code: (define string< string-lessp)
  (define string> string-greaterp)
  
  (define +
    (let ((old+ +))
      (lambda xs (foldl old+ 0 xs))))
  
negative.code:       (proc (car list)
              (foldr proc init (cdr list)))
        init))
  
  (define (unary-map proc list)
    (foldr (lambda (x rest) (cons (proc x) rest))
  