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From: "B. Pym" <Nobody447095@here-nor-there.org>
Newsgroups: comp.lang.lisp,comp.lang.scheme
Subject: Re: simple loop question
Date: Tue, 3 Sep 2024 07:29:30 -0000 (UTC)
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Lars Brinkhoff wrote:

> > use LOOP to collect random integers into a list until the sum of that
> > list exceeds a constant (say 50).
> 
> (loop for x = (random 10) collect x sum x into y until (> y 50))

Gauche Scheme

(let1 y 0 (collect-till x (random 10) (> (inc! y x) 50)))
  ===>
(7 9 4 0 6 4 1 3 2 7 0 7 0 1)


Given:

(use srfi-27) ;; random-integer

(define random random-integer)

(define-syntax collect-till
  (syntax-rules ()
    [(collect-till v expr0 expr1)
     (let ((res '()))
       (let go ((v expr0))
         (set! res (cons v res))
         (if expr1 (reverse res) (go expr0))))]))

(collect-till x (random 10) (even? x))
  ===>
(7 1 6)