Simplify stream-unfolds further, based on Mark H. Weaver's feedback.

* module/srfi/srfi-41.scm (stream-unfolds): Don't use a promise to
  hold the result of the generator call. Originally I did that to
  avoid calling the generator more times than necessary, but Mark
  demonstrated that this code simplification doesn't affect that.

1 files changed, 2 insertions, 6 deletions

diff --git a/module/srfi/srfi-41.scm b/module/srfi/srfi-41.scm
index fd5ec32e2..45b03ad3b 100644
--- a/module/srfi/srfi-41.scm
+++ b/module/srfi/srfi-41.scm
@@ -395,12 +395,8 @@
 
 (define (stream-unfolds gen seed)
   (define-stream (generator-stream seed)
-    ;; This uses delay/force, not stream-delay/stream-force, since only
-    ;; the built-in version supports multiple-value results.
-    (define promise (delay (gen seed)))
-    (stream-cons (receive (_ . items) (force promise)
-                   (list->vector items))
-                 (generator-stream (first-value (force promise)))))
+    (receive (next . items) (gen seed)
+      (stream-cons (list->vector items) (generator-stream next))))
   (define-stream (make-result-stream genstrm index)
     (define head (vector-ref (stream-car genstrm) index))
     (define-stream (tail) (make-result-stream (stream-cdr genstrm) index))