Re: simple loop question

B. Pym wrote:

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
 
(use srfi-27 :only (random-integer))
(define random random-integer)

Not too efficient.

(collect-till (_ z) (random 10) (> (apply + z) 50))


Given:

(define-syntax collect-till
  (syntax-rules ()
    [ (collect-till (x bag) expr test)
      (collect-till (x bag) expr test #f) ]
    [ (collect-till (x bag) expr test include-ender)
      (let go ((bag '()))
        (let ((x expr))
          (if test
            (if include-ender
              (reverse (cons x bag))
              (reverse bag))
            (go (cons x bag))))) ]
    [ (collect-till x expr test)
      (collect-till (x bag) expr test) ]
    [ (collect-till x expr test include-ender)
      (collect-till (x bag) expr test include-ender) ] ))