transit-char-closure.lisp

(deftype transit-char () `(or character (eql ε)))

(defun transit-char-closure (fa-states-prev fa-states-next Δ transit-char)
  "Starting with and including FA-STATES-PREV, add all states reachable by TRANSIT-CHAR via map data structure Δ, to (=>) FA-STATES-NEXT."
  (declare (type sets:set fa-states-prev fa-states-next)
	   (type maps:map Δ)
	   (type transit-char transit-char))
  (sets:set-do-elements (state-prev fa-states-prev fa-states-next); => fa-states-next
    (unless (sets:set-get-element state-prev fa-states-next); If we haven't already looked at this state:
      (sets:set-add-element state-prev fa-states-next); Add current state-prev state to fa-states-next.
      (a:when-let ((state-prev->states (maps:map-get `(,state-prev ,transit-char) Δ))); If set of reachable states exists, 
	(transit-char-closure state-prev->states fa-states-next Δ transit-char))))); recurse to add them and what they can reach too.