From: Witold Baryluk <baryluk-ruby-redmine@...>
Date: 2011-09-26T12:31:40+09:00
Subject: [ruby-core:39722] [Ruby 1.8 - Bug #5367][Open] Floating point number display problem


Issue #5367 has been reported by Witold Baryluk.

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Bug #5367: Floating point number display problem
http://redmine.ruby-lang.org/issues/5367

Author: Witold Baryluk
Status: Open
Priority: Normal
Assignee: 
Category: 
Target version: 
ruby -v: ruby 1.8.7 (2011-06-30 patchlevel 352) [i486-linux] 


Hi,
I'm not really an Ruby user/developer, but noticed this with irb1.8 from Debian sid.


irb(main):005:0> 9007199254740994.0 
=> 9.00719925474099e+15
irb(main):006:0> 9007199254740994.0 -  9.00719925474099e+15
=> 4.0


It looks that Ruby do not convert floating point numbers to decimal/scientific notation correctly (preserving precisly value) by default. I think it is good behavior to preserve value 100% by default, as it can lead to nasty bugs otherwise.

It is quite common bug in various libraries, and known correct (not just hacks) solutions can be find on the Internet.

$ irb1.8 -v
irb 0.9.5(05/04/13)

$ dpkg -l ruby1.8
ii  ruby1.8                                               1.8.7.352-2                                Interpreter of object-oriented scripting language Ruby 1.8

$ uname
Linux sredniczarny 3.0.0-1-686-pae #1 SMP Sat Aug 27 16:41:03 UTC 2011 i686 GNU/Linux

$ cat /proc/cpuinfo | egrep 'model|flags|fpu'
model		: 13
model name	: Intel(R) Pentium(R) M processor 1.73GHz
fpu		: yes
fpu_exception	: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov clflush dts acpi mmx fxsr sse sse2 ss tm pbe nx up bts est tm2


Thanks.




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