From Newsgroup: comp.lang.scheme

I've got this line:
|2|Dollars|23-dec-1999|Idaho|

And I want to sellect the date (23-dec-1999). If I try with this:
(loop repeat 3 do
(setf Position1 (search "|" line)))

I get Position1=0. I would like to 'jump' the first two '|'
characters, in order to get Position1=10. Afterwards, I could use
'subseq' command, but I am not able.

A couple of points:

a) Make sure you have established a valid lexical binding for
variables you set with setf/setq.

b) Use position instead of search, because you are really just looking
for the position of a single character in a string, not doing a
substring search, which is more expensive.

c) Take a look at the start keyword parameter to position.

That gets you to

(defun get-field-from-line (field line)
"Returns a copy of the given field (0 based index) from the line.
Fields are separated by '|'. If there are fewer fields in line than
field, nil is returned."
(loop for start = 0 then (1+ position)
for position = (and start (position #\| line :start start))
repeat field
when (null position)
do (return nil)
finally
(return (subseq line start position))))

Gauche Scheme

(use text.tr) ;; string-tr

(define (get-field-from-line field line)
;; Convert each "|" to a newline character.
(let1 str (string-tr line "|" "\n")
(with-input-from-string str
(lambda()
(dotimes (field) (read-line))
(read-line)))))

(get-field-from-line 3 "|2|Dollars|23-dec-1999|Idaho|")
===>
"23-dec-1999"
--
[T]he problem is that lispniks are as cultish as any other devout group and basically fall down frothing at the mouth if they see [heterodoxy].
--- Kenny Tilton
The good news is, it's not Lisp that sucks, but Common Lisp. --- Paul Graham --- Synchronet 3.21a-Linux NewsLink 1.2