Re: Style question: LOOP and multiple values

Edi Weitz wrote:

I wanted to write a function that reads whitespace-separated numbers
from a string, i.e. given a string like "1 2 3 4" I wanted my function
to return the list (1 2 3 4).
 
Two different solutions came to mind:
 
  (defun foo1 (string)
    (loop for start = 0 then pos
          for (object pos) = (multiple-value-list
                               (read-from-string string nil nil :start start))
          while object
          collect object))
 
  (defun foo2 (string)
    (let ((start 0) object result)
      (loop
        (multiple-value-setq (object start)
          (read-from-string string nil nil :start start))
        (unless object
          (return-from foo2 (nreverse result)))
        (push object result))))

Scheme

(define (read-em)
  (define x (read))
  (if (eof-object? x) () (cons x (read-em))))

(with-input-from-string "2 3 4 5" read-em)

  ===>
(2 3 4 5)