From 5b20a1398befac93116d69112e12c21533667927 Mon Sep 17 00:00:00 2001
From: nobu <nobu@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Wed, 12 May 2010 06:04:59 +0000
Subject: * ext/bigdecimal/lib/bigdecimal/math.rb (BigMath#log): improved  
 precision and performance. [ruby-dev:41295]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@27747 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 ext/bigdecimal/lib/bigdecimal/math.rb | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

(limited to 'ext/bigdecimal')

diff --git a/ext/bigdecimal/lib/bigdecimal/math.rb b/ext/bigdecimal/lib/bigdecimal/math.rb
index 07efcbe099..41fc69f66c 100644
--- a/ext/bigdecimal/lib/bigdecimal/math.rb
+++ b/ext/bigdecimal/lib/bigdecimal/math.rb
@@ -190,8 +190,10 @@ module BigMath
     one = BigDecimal("1")
     two = BigDecimal("2")
     n  = prec + BigDecimal.double_fig
-    if (expo = x.exponent) < 0
+    if (expo = x.exponent) < 0 || expo >= 3
       x = x.mult(BigDecimal("1E#{-expo}"), n)
+    else
+      expo = nil
     end
     x  = (x - one).div(x + one,n)
     x2 = x.mult(x,n)
@@ -206,7 +208,7 @@ module BigMath
       y += d
     end
     y *= two
-    if expo < 0
+    if expo
       y += log(BigDecimal("10"),prec) * BigDecimal(expo.to_s)
     end
     y
-- 
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