From f8a5f7e004d8db8baf5d6b1b0475b90eeb41bf8e Mon Sep 17 00:00:00 2001
From: Alex Shinn <ashinn@users.noreply.github.com>
Date: Sun, 14 Apr 2013 04:59:49 +0000
Subject: [PATCH] exact-integer-sqrt should continue the babylonian method in
 scheme. The estimate given by the C code could be off by a large margin when
 the result is inexact, converging far too slowly if we use simple increments
 in Scheme.

---
 lib/scheme/extras.scm | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/scheme/extras.scm b/lib/scheme/extras.scm
index d7f70393..8dcb04df 100644
--- a/lib/scheme/extras.scm
+++ b/lib/scheme/extras.scm
@@ -61,7 +61,7 @@
         (let lp ((res (inexact->exact (truncate res))))
           (let ((rem (- x (* res res))))
             (if (negative? rem)
-                (lp (- res 1))
+                (lp (quotient (+ res (quotient x res)) 2))
                 (values res rem)))))))
 
 ;; Adapted from Bawden's algorithm.