anchor.diff:   * (defun prefixp (prefix lst &key (test #'eql))
        (cond ((endp prefix) t)
              ((endp lst)    nil)
  -           (t (every (lambda (x y) (funcall test x y))
  -                     prefix lst))))
  -
  - * (defun prefixp (prefix lst &key (test #'eql))
  -     (cond ((endp prefix) t)
  -           ((endp lst)    nil)
              (t (and (funcall test (first prefix) (first lst))
  -                   (prefixp (rest prefix) (rest lst))))))
  -
  - * (defun prefixp (prefix lst &key (test #'eql))
  -     (cond ((endp prefix) t)
  -           ((endp lst)    nil)
  -           (t (loop for s in prefix
  -                    for x in lst
  -                    always (funcall test s x)))))"
  +                   (prefixp (rest prefix) (rest lst))))))"
     :reference "
    * http://www.geocities.jp/m_hiroi/clisp/index.html"
     :test-env
  
positive.code:    (=>? (prefixp '(1 2 3) '())            NIL)
     (=>? (prefixp '(0 1 2 3 4) '(1 2 3))   NIL)
     (=>? (prefixp '(0 1 2 3 4) '(2 3 4))   NIL)
     (=>? (prefixp '(0 1 2 3) '(0 1 2 3 4)) T))
    )
  
negative.code:    (prefixp '(0 1 2 3 4) '(1 2 3))   => NIL
     (prefixp '(0 1 2 3 4) '(2 3 4))   => NIL
     (prefixp '(0 1 2 3) '(0 1 2 3 4)) => T
     (prefixp '(3 4 5) '(3 4))         => NIL
  "
    :hint
    nil
  