As for files: the lib/scanner.arc library allows you to treat input streams (e.g. input files) as if they were a list of characters, which is what treeparse accepts (treeparse can work with "real" lists and scanners).

Treeparse usually returns a list of characters, but this behavior can be modified by using a 'filt parser.

Just off the top of my head (untested!):

  (require "lib/scanner.arc")
  (require "lib/treeparse.arc") ; could use cps_treeparse.arc
  (let (list-str newline line oneline lastline allparse) nil
    ; converts a list of chars to a string
    (= list-str
       [string _])
    ; support \r\n, \n\r, \n, and \r
    (= newline
       ; alt & seq's semantics should be obvious
       (alt
         (seq #\return #\newline)
         (seq #\newline #\return)
         #\newline
         #\return))
    (= line
       ; lots of characters that could be anything...
       ; but *not* newlines!
       (many (anything-but newline)))
    (= oneline
       (seq line
            newline)))
    ; in case the last line doesn't end in newline
    (= lastline
       line)
    (= allparse
       (seq
         ; many is greedy, but will still pass
         ; if there are none
         (many
           ; the filter function has to return a list
           (filt [list (list-str _)]
             oneline))
         ; might not exist; will still pass whether
         ; it exists or not
         (maybe
           (filt [list (list-str _)]
             lastline))))
    (def lines-from-scanner (s)
      (parse allparse s)))
  (def lines-from-file (f)
    (w/infile s f
      (lines-from-scanner (scanner-input s))))