Parsing a comma separated string in lisp

Question

I am trying to parse a comma separated string with Common lisp with the function below. For (separate-on-comma "a,b,c") I would expect the output ("a" "b" "c") but instead I get ("c" "c" "c"). What do I miss here?

(defun separate-on-comma (line)
    (loop
       with fields = () 
       with field = (make-array 0 :element-type 'character :adjustable t :fill-pointer 0)
       for x across line
       when (char= x #\,)        
       do (push field fields)
       and do (setf (fill-pointer field) 0)
       else
       do (vector-push-extend x field)
       finally 
     (push field fields)
     (return fields)))

Thanks.

Alternative: use the split-sequence library. Alternative implementation: use position and subseq in a loop. — Svante
– Svante, Commented Feb 27, 2015 at 0:00
> (ql:quickload :split-sequence) > (split-sequence:split-sequence #\, "a,b,c") ("a" "b" "c") — Baggers
– Baggers, Commented Feb 27, 2015 at 12:07
(progn (ql:quickload "cl-ppcre") (cl-ppcre:split "," "a,b,c")) >("a" "b" "c") Now you can even use regexps for splitting a string. — Sim
– Sim, Commented Feb 28, 2015 at 21:09

Rainer Joswig · Accepted Answer · 2015-02-26 22:20:09Z

4

You are working only with one field array. That's okay. But you better copy it when you push it to the fields list variable. Use copy-seq.

Alternatively create a new field array once you pushed the old one onto the fields list.

answered Feb 26, 2015 at 22:20

Rainer Joswig

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