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;;;
;;;  Code for using a DFA with file I/O.
;;;
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(defun accept-first-from-file (dfa infile)
  "Call accept-first-from-stream, reading data from infile."
  (with-open-file (instream infile)
    (accept-first-from-stream dfa instream)))

(defun accept-first-from-stream (dfa stream)
  "Reads inputs from stream and returns the first one that 
   the dfa accepts.  Returns NIL if end-of-file is reached without
   accepting any inputs.
  "
  (let ((input (read stream nil :EOF)))
    (format t "~&Input: ~S~%" input)
    (cond ((eq input :EOF) nil)
          ((accepts input dfa) input)
          (t (accept-first-from-stream dfa stream)))))

(defun filter-list-using-dfa (inputs dfafile outfile)
  "Runs list of inputs through the DFA in dfafile, 
   writing out the ones the DFA accepts to outfile.
  "
  (with-open-file (instream dfafile)
     (let ((dfa (read instream)))
       (with-open-file (outstream outfile :direction :output)
	   (mapcar #'(lambda (x) 
		       (if (accepts x dfa) 
			   (format outstream "~S~%" x)))
		   inputs)))))

(defun it-filter-list-using-dfa (inputs dfafile outfile)
  "Same as filter-list-using-dfa but iterative, using dolist."
  (with-open-file (instream dfafile)
     (let ((dfa (read instream)))
       (with-open-file (outstream outfile :direction :output)
	   (dolist (x inputs)
	      (if (accepts x dfa) 
		  (format outstream "~S~%" x)))))))


(defun filter-file-using-dfa (dfafile infile outfile)
  "Filters the inputs in infile, writing to outfile only
   those accepted by the DFA in dfafile.  Uses 'do' for iteration.
  "
)