[Guile-commits] GNU Guile branch, srfi-41, updated. v2.0.7-207-g90fbdc1

[Chris K. Jester-Young]

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http://git.savannah.gnu.org/cgit/guile.git/commit/?id=90fbdc109e93620aeacba02507ccc02b2a2baa3b

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- Log -----------------------------------------------------------------
commit 90fbdc109e93620aeacba02507ccc02b2a2baa3b
Author: Chris K. Jester-Young <address@hidden>
Date:   Mon Mar 18 12:21:37 2013 -0400

    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. This means the generator
      will always get called once more than necessary, but it does make
      the code somewhat simpler, and the saved generator call probably
      wasn't worth the added code complexity.

-----------------------------------------------------------------------

Summary of changes:
 module/srfi/srfi-41.scm |    8 ++------
 1 files changed, 2 insertions(+), 6 deletions(-)

diff --git a/module/srfi/srfi-41.scm b/module/srfi/srfi-41.scm
index fd5ec32..45b03ad 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))


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