anchor.diff:  (in-package :lem)
   
   (export '(define-command
  -          find-command
             exist-command-p))
   
   (defvar *command-table* (make-hash-table :test 'equal))
  
positive.code: 
  (defun all-command-names ()
    (alexandria:hash-table-keys *command-table*))
  
  (defun exist-command-p (str)
    (if (find-command str) t nil))
  
negative.code:                         (car arg-descripters))
                   (apply #',fn-name ,arguments)))))))
  
  (defun exist-command-p (command-name)
    (not (null (gethash command-name *command-table*))))
  
  (defun find-command-symbol (name)
    (cdr (gethash name *command-table*)))
  