From: Zachary Scott <e@...>
Date: 2014-01-09T17:32:52-05:00
Subject: [ruby-core:59673] Re: [ruby-trunk - Bug #9170] Math.sqrt returns	different types when mathn is included;	breaks various gems - this bug can be reproduced in Ruby 1.8 as well

I will check the docs and see if I can fix it.

> On Jan 6, 2014, at 12:44 AM, "kranzky (Jason Hutchens)" <JasonHutchens@gmail.com> wrote:
> 
> 
> Issue #9170 has been updated by kranzky (Jason Hutchens).
> 
> 
> mrkn (Kenta Murata) wrote:
>> It's not a bug.
> 
> I'm a middle-man here, but I have gem maintainers claiming that it is a bug, because the documentation for Math.sqrt() indicates that it returns a Float, and that it's therefore OK to assume that it can be treated as a Float by the caller. Ref: http://ruby-doc.org/core-2.1.0/Math.html#method-c-sqrt
> ----------------------------------------
> Bug #9170: Math.sqrt returns different types when mathn is included; breaks various gems - this bug can be reproduced in Ruby 1.8 as well
> https://bugs.ruby-lang.org/issues/9170#change-44105
> 
> Author: kranzky (Jason Hutchens)
> Status: Feedback
> Priority: Normal
> Assignee: 
> Category: core
> Target version: next minor
> ruby -v: ruby 2.0.0p247 (2013-06-27 revision 41674) [x86_64-darwin12.2.1]
> Backport: 1.9.3: UNKNOWN, 2.0.0: UNKNOWN
> 
> 
> Math.sqrt() usually returns a Float or throws an exception. Some gems rely on this behaviour (e.g. by calling nan? on the results of a calculation that includes a sqrt).
> 
> After requiring mathn, Math.sqrt() returns an Integer in some cases (when the results of the sqrt would be a whole number).
> 
> Here is a transcript that demonstrates the problem:
> 
> $ rvm use ree
> Using /Users/jason/.rvm/gems/ree-1.8.7-2012.02
> $ ruby -v
> ruby 1.8.7 (2012-02-08 MBARI 8/0x6770 on patchlevel 358) [i686-darwin12.1.0], MBARI 0x6770, Ruby Enterprise Edition 2012.02
> $ ruby -e "puts Math.sqrt(4).nan?"
> false
> $ ruby -e "require 'mathn'; puts Math.sqrt(4).nan?"
> -e:1: undefined method `nan?' for 2:Fixnum (NoMethodError)
> $ rvm use 1.9.3
> Using /Users/jason/.rvm/gems/ruby-1.9.3-p448
> $ ruby -v
> ruby 1.9.3p448 (2013-06-27 revision 41675) [x86_64-darwin12.2.0]
> $ ruby -e "puts Math.sqrt(4).nan?"
> false
> $ ruby -e "require 'mathn'; puts Math.sqrt(4).nan?"
> -e:1:in `<main>': undefined method `nan?' for 2:Fixnum (NoMethodError)
> $ rvm use 2.0
> Using /Users/jason/.rvm/gems/ruby-2.0.0-p247
> $ ruby -v
> ruby 2.0.0p247 (2013-06-27 revision 41674) [x86_64-darwin12.2.1]
> $ ruby -e "puts Math.sqrt(4).nan?"
> false
> $ ruby -e "require 'mathn'; puts Math.sqrt(4).nan?"
> -e:1:in `<main>': undefined method `nan?' for 2:Fixnum (NoMethodError)
> $ rvm use jruby
> Using /Users/jason/.rvm/gems/jruby-1.7.4
> $ ruby -v
> jruby 1.7.4 (1.9.3p392) 2013-05-16 2390d3b on Java HotSpot(TM) 64-Bit Server VM 1.6.0_51-b11-457-11M4509 [darwin-x86_64]
> $ ruby -e "puts Math.sqrt(4).nan?"
> false
> $ ruby -e "require 'mathn'; puts Math.sqrt(4).nan?"
> NoMethodError: undefined method `nan?' for 2:Fixnum
>  (root) at -e:1
> 
> Here is a discussion of how the bug manifests itself: https://github.com/olbrich/ruby-units/pull/48
> 
> Inclusion of mathn causes issues in RGeo, Alchemist, ActiveShipping and pry-rails
> 
> 
> -- 
> http://bugs.ruby-lang.org/