How to convert a string to list using clisp?

Question

How can i convert the string "1 2 3 4 5 6 7" into the list (1 2 3 4 5 6 7) elegantly? I am using CLISP.

Solution 1

Hint: Take a look at with-input-from-string.

Solution 2

Here is a recursive solution.

    ;Turns a string into a stream so it can be read into a list
    (defun string-to-list (str)
        (if (not (streamp str))
           (string-to-list (make-string-input-stream str))
           (if (listen str)
               (cons (read str) (string-to-list str))
               nil)))

Solution 3

You should use parse-integer in a loop.

For example, using loop:

(let ((string "1 2 3"))
  (loop :for (integer position) := (multiple-value-list 
                                    (parse-integer string
                                                   :start (or position 0)
                                                   :junk-allowed t))
        :while integer
        :collect integer))

⇒ (1 2 3)

If you need better control about the splitting, use the split-sequence or cl-ppcre library.

If you need to parse more general number formats, use the parse-number library.

Libraries are available from Quicklisp.

Solution 4

(with-input-from-string (s "1 2 3 4 5 6 7" :index i :start 0 :end 13)
              (list (read s) (read s) (read s) (read s) (read s) (read s)))
(1 2 3 4 5 6 7)

it works however i feel it is not so elegant as there are many read call .

thanks again!

Solution 5

I think this might work:

(setf s "1 2 3 4 5 6 7")
(setf L-temp (coerce s 'list))

This makes a list with spaces as elements. Remove spaces:

(setf L-final (remove #\Space L-temp))

View more solutions

Comments

[mange]

(with-input-from-string (s "1 2 3 4 5 6 7") (loop for x = (read s nil :end) until (eq x :end) collect x)) should work, but note that it will take "one two three" to a list of symbols rather than a list of strings.

[sçuçu]

additionally, in the above form, in the first list you can replace a string, here "1 2 3 4 5", with a form like (read-line stream), to read a line from a stream yet not yielding a string but a list.

[Svante]

This produces the list (#\1 #\2 #\3 #\4 #\5 #\6 #\7), i. e. a list of digit characters. Aside: don't setf variables that do not exist.

[Indinfer]

I see Svante is correct. I tried again and posted the answer using read-from-string. I'm still beginning to learn Lisp. So, I am curious about not "setf variables that do not exist". Is that a violation of functional style? Or does it make my code more confusing in larger programs?

[Svante]

No, it is just undefined behaviour. You are implicitly creating a global variable that may or may not be special (dynamic). Use defparameter or defvar to create a new globally special variable, or use let (or other constructs introducing a local scope) to create local variables.

[Indinfer]

I appreciate your explanation, Svante. Thank you.