[Guile-commits] GNU Guile branch, stable-2.0, updated. v2.0.9-36-g0690378

[Mark H Weaver]

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- Log -----------------------------------------------------------------
commit 06903786211afd9a554b8f009a37111f729607ee
Author: Mark H Weaver <address@hidden>
Date:   Tue Jul 16 17:38:14 2013 -0400

    Fix R6RS 'fixnum-width'.
    
    Fixes <http://bugs.gnu.org/14879>.
    Reported by Göran Weinholt <address@hidden>.
    
    * module/rnrs/arithmetic/fixnums.scm (fixnum-width): Rewrite to avoid
      inexact arithmetic, and correct the off-by-one error.
    
    * test-suite/tests/r6rs-arithmetic-fixnums.test (fixnum-width): Add
      tests.

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

Summary of changes:
 module/rnrs/arithmetic/fixnums.scm            |    7 +++++--
 test-suite/tests/r6rs-arithmetic-fixnums.test |    8 ++++++++
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/module/rnrs/arithmetic/fixnums.scm 
b/module/rnrs/arithmetic/fixnums.scm
index dbf9ee7..7a5a621 100644
--- a/module/rnrs/arithmetic/fixnums.scm
+++ b/module/rnrs/arithmetic/fixnums.scm
@@ -95,8 +95,11 @@
          (rnrs exceptions (6))
          (rnrs lists (6)))
 
-  (define fixnum-width 
-    (let ((w (inexact->exact (round (/ (log (+ most-positive-fixnum 1)) (log 
2))))))
+  (define fixnum-width
+    (let ((w (do ((i 0 (+ 1 i))
+                  (n 1 (* 2 n)))
+                 ((> n most-positive-fixnum)
+                  (+ 1 i)))))
       (lambda () w)))
 
   (define (greatest-fixnum) most-positive-fixnum)
diff --git a/test-suite/tests/r6rs-arithmetic-fixnums.test 
b/test-suite/tests/r6rs-arithmetic-fixnums.test
index 01a7a89..60c3b87 100644
--- a/test-suite/tests/r6rs-arithmetic-fixnums.test
+++ b/test-suite/tests/r6rs-arithmetic-fixnums.test
@@ -23,6 +23,14 @@
   :use-module ((rnrs exceptions) :version (6))
   :use-module (test-suite lib))
 
+(with-test-prefix "fixnum-width"
+  (pass-if-equal "consistent with least-fixnum"
+      (- (expt 2 (- (fixnum-width) 1)))
+    (least-fixnum))
+  (pass-if-equal "consistent with greatest-fixnum"
+      (- (expt 2 (- (fixnum-width) 1)) 1)
+    (greatest-fixnum)))
+
 (with-test-prefix "fixnum?"
   (pass-if "fixnum? is #t for fixnums" (fixnum? 0))
 


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