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dragolov
PostPosted: Wed Jan 16, 2013 8:42 am 
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I expected 0.3

?
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dwfreed
PostPosted: Wed Jan 16, 2013 8:47 am 
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Joined: Mon Aug 29, 2011 2:34 am
Posts: 77
dragolov wrote:
I expected 0.3

?


Welcome to IEEE 754 double-precision floating point arithmetic. http://en.wikipedia.org/wiki/IEEE_floating_point Basic gist is don't expect anything to ever be exact :) .
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Guspaz
PostPosted: Wed Jan 16, 2013 11:30 am 
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It's been a long time since I touched Haskell in university, but in most languages, I'd say "Don't use double if you need a precise answer, use the language's decimal implementation."
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hoopycat
PostPosted: Wed Jan 16, 2013 1:55 pm 
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Curiously,

Code:
Python 2.6.5 (r265:79063, Oct  1 2012, 22:04:36) 
[GCC 4.4.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> 9.3 - (2 * 4.5)
0.30000000000000071

$ irb -v
irb 0.9.5(05/04/13)
$ irb
irb(main):001:0> 9.3 - (2 * 4.5)
=> 0.300000000000001

$ perl -v

This is perl, v5.10.1 (*) built for x86_64-linux-gnu-thread-multi
...
$ perl -e "print 9.3 - (2 * 4.5);"
0.300000000000001

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Vance
PostPosted: Thu Jan 17, 2013 9:01 am 
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Code:
$ bc -v
bc 1.06
Copyright 1991-1994, 1997, 1998, 2000 Free Software Foundation, Inc.
$ echo 'scale=100; 9.3 - (2 * 4.5)' | bc
.3


:)
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zunzun
PostPosted: Thu Jan 17, 2013 9:18 am 
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Posts: 594
IIRC the latest version of Haskell now makes all internal calculations using Roman numerals instead of binary, negating this problem.

James
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Guspaz
PostPosted: Thu Jan 17, 2013 11:40 am 
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That sounds about right for Haskell.
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