[ruby-core:61155] [ruby-trunk - Bug #9192] Inconsistent comparison between Float and BigDecimal

Issue #9192 has been updated by Wolfgang Teuber.


Marc-Andre Lafortune wrote:
> 2) The implementation is buggy. For example:
> 
>     BigDecimal('0.21611564636388508') == 0.21611564636388508 # => false, should be true

You are exceeding the max precision Float::DIG (http://www.ruby-doc.org/core-2.0.0/Float.html#DIG => "Usually defaults to 15."). Your example uses 17 significant digits, which will ultimately lead to floating point number errors. The issue you described is not related to Gustavo's issue.

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Bug #9192: Inconsistent comparison between Float and BigDecimal
https://bugs.ruby-lang.org/issues/9192#change-45524

* Author: Gustavo Sales
* Status: Open
* Priority: Normal
* Assignee: Kenta Murata
* Category: ext
* Target version: 
* ruby -v:  2.0.0p353 (2013-11-22 revision 43784) [x86_64-darwin11.4.2]
* Backport: 1.9.3: UNKNOWN, 2.0.0: UNKNOWN
----------------------------------------
I was checking a possible inconsistency on ActiveModel and I found situations where comparing BigDecimal to Float differs to comparing Float to BigDecimal.

I have create a simple ruby script to exemplify the problem. The script is attach to this issue and output is as follows:

Instance number 706.05
###########
Instance number 706.06
Inconsistence:
0.70606E3 > 706.06
706.06 < 0.70606E3
=========
Inconsistence:
0.70606E3 <= 706.06
706.06 >= 0.70606E3
=========
###########
Instance number 706.07
Inconsistence:
0.70607E3 < 706.07
706.07 > 0.70607E3
=========
Inconsistence:
0.70607E3 >= 706.07
706.07 <= 0.70607E3
=========
###########
Instance number 706.08
###########

---Files--------------------------------
compare_decimal_float.rb (529 Bytes)


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