I had a task to wrote a function which receives as a parameter the name of a file containing the coefficients of a system of linear equations specified in the form of a rectangular matrix. Using acceptable transformations, bring the system to a triangular appearance. Write the result to a file.

   (bind ?input (open ?input-filename "r"))
   (bind ?output (open ?output-filename "w"))
   (if (not ?input)
      then
      (printout t "Error of opening " ?input-filename crlf)
      (return))
   
   (bind ?matrix (create$))
   (while (not (eq (readline ?input) EOF))
      (bind ?line (readline ?input))
      (if (neq ?line nil)
         then
         (bind ?row (create$))
         (bind ?token "")
         (bind ?len (str-length ?line))
         (loop-for-count (?i 1 (+ 1 ?len)) do
            (bind ?char (str-index ?line ?i))
            (if (str-compare ?char " ")
               then
               (if (neq ?token "")
                  then
                  (bind ?number (string-to-field ?token))
                  (if (numberp ?number)
                     then
                     (bind ?row (create$ ?row ?number))
                     (bind ?token "")))
               else
               (bind ?token (str-cat ?token ?char))))
         (if (neq (length$ ?row) 0)
            then
            (bind ?matrix (create$ ?matrix ?row)))))
   
   (bind ?num-rows (length$ ?matrix))
   (bind ?num-cols (length$ (first$ ?matrix)))

   (loop-for-count (?i 1 (+ 1 ?num-cols)) do
      (loop-for-count (?j ?i (- ?num-rows 1)) do
         (bind ?pivot-row (nth$ ?j ?matrix))
         (bind ?pivot (nth$ ?i ?pivot-row))
         (if (neq ?pivot 0)
            then
            (loop-for-count (?k (+ ?j 1) ?num-rows) do
               (bind ?current-row (nth$ ?k ?matrix))
               (bind ?factor (/ (nth$ ?i ?current-row) ?pivot))
               (bind ?scaled-row (create$))
               (loop-for-count (?l 1 (+ 1 ?num-cols)) do
                  (bind ?new-value (- (* (nth$ ?l ?pivot-row) ?factor) (nth$ ?l ?current-row)))
                  (bind ?scaled-row (create$ ?scaled-row ?new-value)))
               
               (replace$ ?matrix ?k ?k ?scaled-row)
            )
         )
      )
   )

   (foreach ?row ?matrix do
      (bind ?result "")
      (loop-for-count (?i 1 (+ 1 (length$ ?row))) do
         (bind ?element (nth$ ?i ?row))
         (if (neq ?i 1) then (bind ?result (str-cat ?result " "))) 
         (bind ?result (str-cat ?result ?element)) 
      )
      (printout ?output ?result crlf)
   )

   (close ?input) 
   (close ?output) 
)

And this is the error:

`CLIPS> (solve-system "file1" "file3")
[ROUTER1] Logical name 'TRUE' was not recognized by any routers.
[PRCCODE4] Execution halted during the actions of deffunction 'solve-system'.
FALSE`

How can I fix this?

I tried to not bind files but I don’t know how to fix that. Also I thought that the problem may be in the names of files but it wasn’t.