# 2000-1992.2 - is this a known bug? **URL:** \ **Category:** Ruby\ **Created:** [March 7, 2009, 12:05am UTC](https://www.ruby-forum.com/t/2000-1992-2-is-this-a-known-bug/162224 "2009-03-07T00:05:45Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![S2S2S2](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/f08c70/32.png) [@S2S2S2](https://www.ruby-forum.com/u/S2S2S2)\ **Post date:** [March 7, 2009, 12:05am UTC](https://www.ruby-forum.com/t/2000-1992-2-is-this-a-known-bug/162224/1 "2009-03-07T00:05:45Z")
ruby 1.8.7 (2008-08-11 patchlevel 72) [i486-linux] > > 2000-1992.2 > > =\> 7.79999999999995 ---
**Author:** ![S2S2S2](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/f08c70/32.png) [@S2S2S2](https://www.ruby-forum.com/u/S2S2S2)\ **Post date:** [March 7, 2009, 12:11am UTC](https://www.ruby-forum.com/t/2000-1992-2-is-this-a-known-bug/162224/2 "2009-03-07T00:11:37Z")
2009/3/6 S2 [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid): > ruby 1.8.7 (2008-08-11 patchlevel 72) [i486-linux] > > > > 2000-1992.2 > > > =\> 7.79999999999995 [http://docs.sun.com/source/806-3568/ncg\_goldberg.html](http://docs.sun.com/source/806-3568/ncg_goldberg.html) ---
**Author:** ![S2S2S2](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/f08c70/32.png) [@S2S2S2](https://www.ruby-forum.com/u/S2S2S2)\ **Post date:** [March 7, 2009, 12:12am UTC](https://www.ruby-forum.com/t/2000-1992-2-is-this-a-known-bug/162224/3 "2009-03-07T00:12:47Z")
> > > 2000-1992.2 > > > =\> 7.79999999999995 It is known non-bug: [http://docs.sun.com/source/806-3568/ncg\_goldberg.html](http://docs.sun.com/source/806-3568/ncg_goldberg.html) Regards, Rimantas ---
**Author:** ![S2S2S2](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/f08c70/32.png) [@S2S2S2](https://www.ruby-forum.com/u/S2S2S2)\ **Post date:** [March 7, 2009, 4:44am UTC](https://www.ruby-forum.com/t/2000-1992-2-is-this-a-known-bug/162224/4 "2009-03-07T04:44:59Z")
2009/3/6 S2 [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid): > ruby 1.8.7 (2008-08-11 patchlevel 72) [i486-linux] > > > > 2000-1992.2 > > > =\> 7.79999999999995 The use of inexact floating point numbers by default in Ruby (which follows C and most, but not all, other programming languages) is a design choice, not a bug. One might dispute whether or not its a good design choice (personally, I prefer Scheme’s numeric tower and exact numbers by default with conversion to inexact numbers only when an inexact operation is applied to an exact number or an explicit designation of an inexact number is given), but its a point about which people could debate endlessly, and since BigDecimal is at least in the standard library, its not a matter of whether Ruby can do exact math, but just how verbose the code is to do it. ex: require ‘bigdecimal’ require ‘bigdecimal/math’ class BigDecimal # BigDecimal.to\_s is ugly def pretty digits, magnitude = to\_s.split(‘.’)[1].split(‘E’) magnitude=magnitude.to\_i digits.insert(0,‘0’\*[(1-magnitude),0].max) digits.insert([magnitude,1].min,‘.’) end end include BigMath (2000-BigDecimal(‘1992.2’)).pretty =\> “7.8” ---
**Author:** ![S2S2S2](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/f08c70/32.png) [@S2S2S2](https://www.ruby-forum.com/u/S2S2S2)\ **Post date:** [March 7, 2009, 4:56am UTC](https://www.ruby-forum.com/t/2000-1992-2-is-this-a-known-bug/162224/5 "2009-03-07T04:56:05Z")
On Fri, Mar 6, 2009 at 7:42 PM, Christopher D. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > design choice, not a bug. One might dispute whether or not its a good > require ‘bigdecimal’ > end > > include BigMath > > (2000-BigDecimal(‘1992.2’)).pretty > =\> “7.8” Or, while that works for the case presented, if you want it to work right in general: class BigDecimal def pretty return to\_i.to\_s if self==to\_i digits, magnitude = to\_s.split(‘.’)[1].split(‘E’) magnitude = magnitude.to\_i digits.insert(0,‘0’\*[(1-magnitude),0].max) digits.insert([magnitude, 1].max,‘.’) end end ---
**Author:** ![S2S2S2](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/f08c70/32.png) [@S2S2S2](https://www.ruby-forum.com/u/S2S2S2)\ **Post date:** [March 7, 2009, 5:17am UTC](https://www.ruby-forum.com/t/2000-1992-2-is-this-a-known-bug/162224/6 "2009-03-07T05:17:42Z")
Hi, 2009/3/7 Christopher D. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid): > design choice, not a bug. One might dispute whether or not its a good > require ‘bigdecimal’ > end > > include BigMath > > (2000-BigDecimal(‘1992.2’)).pretty > =\> “7.8” Why not use BigDecimal.to\_s(‘F’) ? Refer to [http://www.ruby-doc.org/stdlib/libdoc/bigdecimal/rdoc/classes/BigDecimal.html#M000032](http://www.ruby-doc.org/stdlib/libdoc/bigdecimal/rdoc/classes/BigDecimal.html#M000032) Regards, Park H. ---
**Author:** ![S2S2S2](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/f08c70/32.png) [@S2S2S2](https://www.ruby-forum.com/u/S2S2S2)\ **Post date:** [March 7, 2009, 5:28am UTC](https://www.ruby-forum.com/t/2000-1992-2-is-this-a-known-bug/162224/7 "2009-03-07T05:28:14Z")
On Fri, Mar 6, 2009 at 8:15 PM, Heesob P. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > > Â Â digits.insert(0,‘0’\*[(1-magnitude),0].max) > > Refer to [http://www.ruby-doc.org/stdlib/libdoc/bigdecimal/rdoc/classes/BigDecimal.html#M000032](http://www.ruby-doc.org/stdlib/libdoc/bigdecimal/rdoc/classes/BigDecimal.html#M000032) Because that would be sane? No, seriouly, I knew there was a BigDecimal formatter somewhere that I’d seen (and even used, though not recently), but I thought it was external. Clearly, it’s better to use that than to try to reinvent the wheel.