```けいじゅ＠日本ラショナルソフトウェアです.

In [ruby-math:00774] the message: "[ruby-math:00774] Forward:
matrix.rb bug", on Nov/22 01:51(JST) Yukihiro Matsumoto writes:

>まつもと ゆきひろです

>要旨:
>m = Matrix[[10, 5,10],
>           [10, 5, 0],
>           [ 1, 1, 1]]
>のとき
>
>m.det
>
>が50になるが、-50ではないかと。

えー. これは例の, 1/2 = 0 の副作用ですね.

るか, require "mathn"をしてください. となりますです...

# 今の結果は, 一応ruby的には正しい結果だと思います.

>(私のところでは100になるんですが...)
>
>------- Start of forwarded message -------
>Delivered-To: matz / netlab.jp
>Date: Thu, 21 Nov 2002 09:30:25 -0700
>From: Hans Fugal <hans / fugal.net>
>Subject: matrix.rb bug
>To: matz / netlab.jp
>
>Consider the following matrix
>m = Matrix[[10, 5,10],
>           [10, 5, 0],
>           [ 1, 1, 1]]
>
>The determinant should be -50, according to my HP calculator.  m.det
>returns 50.
>
>If I construct the matrix out of floats, m.det returns -50.0. If I
>include one float in the matrix it may or may not return the right
>answer, depending on where the float is.
>
>some irb output:
>irb(main):001:0> require 'matrix'
>true
>irb(main):002:0> Matrix[[10,5,10],[0,5,10],[1,1,1]].det
>50
>irb(main):003:0> Matrix[[10,5,10],[0,5,10],[1.0,1,1]].det
>- -50.0
>irb(main):004:0> Matrix[[10,5,10],[0,5,10],[1,1.0,1]].det
>- -50.0
>irb(main):005:0> Matrix[[10,5,10],[0,5,10],[1,1,1.0]].det
>50.0
>
>- --
> Hans Fugal                 | If more of us valued food and cheer and
> http://hans.fugal.net/     | song above hoarded gold, it would be a
> jabber: hans / fugal.net     | merrier world.
>                            |         -- J.R.R. Tolkien
>- ---------------------------------------------------------------------
>GnuPG Fingerprint: 6940 87C5 6610 567F 1E95  CB5E FC98 E8CD E0AA D460
>
>------- End of forwarded message -------
>

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..............................石塚 圭樹＠日本ラショナルソフトウェア...
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