From: Milind Pandit <redmine@...>
Date: 2010-07-08T16:32:45+09:00
Subject: [ruby-core:31121] [Backport #3550] Floating Point Representation Prevents Raising to Fractional Power

Backport #3550: Floating Point Representation Prevents Raising to Fractional Power
http://redmine.ruby-lang.org/issues/show/3550

Author: Milind Pandit
Status: Open, Priority: Normal

Not sure why this literal float can be raised successfully to a fractional power, but when assigned to a variable, it returns NaN.

$ ruby --version
ruby 1.8.7 (2009-06-12 patchlevel 174) [universal-darwin10.0]
$ irb
-2.21792114695341 ** 0.1
=> -1.08291560040828
>> -2.21792114695341 ** 1.1
=> -2.40182141051126
>> a = -2.21792114695341
=> -2.21792114695341
>> a ** 0.1
=> NaN # Expected: -1.08291560040828
>> a ** 1.1
=> NaN # Expected: -2.40182141051126
>> -2.21792114695341.to_f ** 1.1
=> NaN # Expected: -1.08291560040828
>> -2.21792114695341.to_f ** 0.1
=> NaN # Expected: -2.40182141051126
>> a - -2.21792114695341
=> 0.0
>> (a - -2.21792114695341).zero?
=> true


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