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* ext/bigdecimal/lib/bigdecimal/math.rb (BigMath#log): improved

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precision and performance. [ruby-dev:41295]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@27747 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
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nobu 2010-05-12 06:04:59 +00:00
parent 851a023843
commit 5b20a1398b
2 changed files with 9 additions and 2 deletions
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5
ChangeLog
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@ -1,3 +1,8 @@
Wed May 12 15:04:57 2010 Nobuyoshi Nakada <nobu@ruby-lang.org>
* ext/bigdecimal/lib/bigdecimal/math.rb (BigMath#log): improved
precision and performance. [ruby-dev:41295]
Wed May 12 11:39:10 2010 NAKAMURA Usaku <usa@ruby-lang.org>
* ext/socket/extconf.rb: test all IPPROTO_* constants for recent Win32

6
ext/bigdecimal/lib/bigdecimal/math.rb
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@ -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