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;;; pregexp7.scm - 
; extract all lines in a file that match a regex and write them to another file

(load "pregexp.scm")

; note: In PLT Scheme use (open-output-file output-file-name 'replace) 
; instead "open-output-file-writeover" 

(define (open-output-file-writeover out-file)
   (if (file-exists? out-file) 
      (delete-file out-file))
   (open-output-file out-file)
  )

(define (match-lines-to-file pattern in-file out-file)
   (let ((out-port (open-output-file-writeover out-file))
         (in-port (open-input-file in-file))
         (i 0))
            (do ((line " " (read-line in-port))) 
                ((eof-object? line) #t)
                (let ((answer (pregexp-match pattern line)))
                   (if (not answer)
	              '()
                      (display (format "~%~A:~A" i line) out-port) ))
                (set! i (+ i 1))
            )
            (close-input-port in-port)
            (close-output-port out-port)
   ) 
)

;-----------------------------------------------------------------------
; run program
(define out-file "adieu_de_sucy.txt")
(define in-file "adieu10.txt")
(define pattern "de Sucy")
(match-lines-to-file pattern in-file out-file)