anchor.diff:  (in-package :lem)
   
   (export '(start-line-p
  -          tail-line-p
  +          end-line-p
             bolp
             eolp
             bobp
  
positive.code:   (beginning-of-line)
    (if (plusp n)
        (dotimes (_ n t)
          (when (tail-line-p)
            (end-of-line)
            (return))
          (incf (current-linum)))
  
negative.code:   (and (start-line-p) (bolp)))
  
  (defun eobp ()
    (and (end-line-p) (eolp)))
  
  (defun insert-char (c &optional (n 1))
    (dotimes (_ n t)
  