CODEWITHSUNDEEP
lispcommon-lisp
Sarriman
Sarriman

Reputation: 422

Store list from file input stream, in a variable in LISP

I have lets say the following list in a .txt file

(5 3 1)

All i am trying with following source code is to store the above list in a variable in LISP. Until the first format everything seems right. But then i realize that *originalStateVar* is not getting treated as a list with 3 atoms but as a list with 1 atom. Source code follows:

(defvar *originalStateVar*)
(defun fileInput ()
  (let ((i 1)(in (open *originalStateLocation* :if-does-not-exist nil)))
        (when in
            (loop
                for line = (read-line in nil)
                while line do 
                    (format t "~a~%" line)                ;debug line
                    (format t "i is <~a>~%" i)            ;debug line
                    (setf *originalStateVar* (list line)) ;storing list in variable
                    (setf i (+ i 1)))                     ;debug line
            (close in))
        (format t "originalStateVar is <~a>" (car *originalStateVar*))
        (format t "second element originalStateVar is <~a>~%" (cadr *originalStateVar*))
        (format t "third element originalStateVar is <~a>~%" (caddr *originalStateVar*))))

The output of the above code though is:

(5 3 1)
i is <1>
first element originalStateVar is <(5 3 1)>
second element originalStateVar is <NIL>
third element originalStateVar is <NIL>

All i can tell is that it stores the (5 3 1) as a single atom in a list, so it becomes something like ((5 3 1)) and that's why cadr returns NIL.

Any help on how to make *originalStateVar* get treated that way, would be greatly appreciated!

Upvotes: 0

Views: 373

Answers (1)

Rainer Joswig
Rainer Joswig

Reputation: 139251

  • use WITH-OPEN-FILE instead of OPEN
  • use READ instead of READ-LINE

Example:

CL-USER 11 > (let ((*read-eval* nil))
               (with-open-file (in "/tmp/test.data")
                 (read in)))
(1 2 3)

CL-USER 12 > (let ((*read-eval* nil))
               (with-open-file (in "/tmp/test.data")
                 (describe (read in))))

(1 2 3) is a LIST
0      1
1      2
2      3

Upvotes: 5

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