Re: Is there a better way to read multiple values from a string

Pascal J. Bourguignon wrote:

I have a strings like "0  2  0  1".  The number of values may vary, but
they all can be read using READ
>
Right now I do the following
(loop
     :for (x pos) = (multiple-value-list
     (read-from-string first-line nil nil :start (or pos 0)))
     :while x
     :collect x)
>
>
Is there a more idiomatic way to read all the tokens in the string and
return them as a list?

 
    (with-input-from-string (in string)
      (loop :for n = (read in nil  nil)
            :while n :collect n))

If we are allowed to use a collector, then the loop
becomes much shorter.  Compare:

(loop :for n = (read in nil  nil) :while n :collect n))
(until (eof-object? (bag (read))))

Gauche Scheme:

(define bag (mlistbag))

(with-input-from-string "0 4 2 5"
  (lambda()
    (until (eof-object? (bag (read))))))

;; Remove the eof-object.
(drop-right (bag) 1)
  ===>
(0 4 2 5)

Given:

(define (mbag init func :optional (pass-through #f))
  (let ((val init) (func func) (pass-through pass-through))
    (lambda args
      (if (null? args)
        val
        (begin
          (set! val
            ;; A "kons" may have been supplied.
            ((if (null? (cdr args)) func (cadr args))
              (car args) val))
          (if pass-through
            (car args)
            val))))))

(define (mlistbag :optional (pass-through #t))
  (let ((bag (mbag '() cons pass-through)))
    (lambda args
      (if (null? args)
        (reverse (bag))
        (apply bag args)))))