From: Yukihiro Matsumoto <matz@...>
Date: 2008-04-12T21:28:15+09:00
Subject: [ruby-dev:34357] fw: Bug in ruby complex module

まつもと ゆきひろです

見落としてましたが、昨年末に「Complexの除算にバグがある」と
いうメールがruby-coreに来てました。[ruby-talk:285292]

現状のC組み込みのcomplexでも同様の「問題」があります。ただ、
私にはこれが本当に問題なのかどうか判断できませんので、意見を
聴かせてください。

Date: Sun, 30 Dec 2007 02:18:36 +0900
Posted: Sat, 29 Dec 2007 18:18:38 +0100
From: Tommy Nordgren

Transcript :
emac$ irb
 >> require 'complex'
=> true
 >> cc = Complex(Float::MAX/2, Float::MAX / 2)
=> Complex(8.98846567431158e+307, 8.98846567431158e+307)
 >> cc / cc
=> Complex(NaN, NaN)
 >> require 'cpfixup'
=> true
 >> cc / cc
=> Complex(1.0, 0.0)
 >> exit
Work Directory: ~ :
emac$
Th source of the fix (in a file called 'cpfixup.rb' in my home  
directory is

require 'complex'

class Complex < Numeric

   def / (other)
     if other.kind_of?(Complex)
       magn = other.abs
       tmp = Complex.new(other.real/magn , other.image/magn)
       self * tmp.conjugate / magn
     elsif Complex.generic?(other)
       Complex(@real/other, @image/other)
     else
       x, y = other.coerce(self)
       x / y
     end
   end
end

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