[cclan-list] adding system-loaded-p to ASDF

[Gary K. <gw...@me...>]

AFAIK, there is no _easy_ way to tell if a system has been loaded in  
ASDF. #'find-system lets me know if a system is defined but I have to  
look at operation-done-p to know whether or not it has been loaded.  
The following adds #'system-loaded-p and two methods on #'operation- 
done-p to make it easier to use by converting symbols into instances  
of reasonable classes.

(in-package #:asdf)

(defmethod operation-done-p ((o symbol) (c t))
  (operation-done-p (make-instance o) c))

(defmethod operation-done-p ((o t) (c symbol))
  (operation-done-p o (find-system c)))

(defun system-loaded-p (system)
  (operation-done-p 'load-op (find-system system)))

If there is no disagreement, I'll add some documentation and tests and  
commit.
--
Gary Warren King, metabang.com
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