# \[Bug #913\] mathn $B$7$?\>l9g!"(Bsqrt(NaN) $B$,J#AG?t$K$J$k(B

**URL:** <https://www.ruby-forum.com/t/bug-913-mathn-b-7-l9g-bsqrt-nan-b-j-ag-t-k-j-k-b/156169>\
**Category:** Development\
**Created:** [December 22, 2008, 3:47am UTC](https://www.ruby-forum.com/t/bug-913-mathn-b-7-l9g-bsqrt-nan-b-j-ag-t-k-j-k-b/156169 "2008-12-22T03:47:51Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![Yuki\_S](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/a6a055/32.png) [@Yuki\_S](https://www.ruby-forum.com/u/Yuki_S)\
**Post date:** [December 22, 2008, 3:47am UTC](https://www.ruby-forum.com/t/bug-913-mathn-b-7-l9g-bsqrt-nan-b-j-ag-t-k-j-k-b/156169/1 "2008-12-22T03:47:51Z")

</div>

e$B%A%1%C%He(B #913 e$B$,99?7$5$l$^$7$?!#e(B (by Yuki S.)

e$B$?$V$s!"$3$s$J46$8$@$H;W$$$^$9!#%3%\_%C%H$7$F$h$$$G$9$+e(B? \<  
e$B@PDM$5$se(B

diff --git a/lib/mathn.rb b/lib/mathn.rb  
index 48cb99f…0241f57 100644  
— a/lib/mathn.rb  
+++ b/lib/mathn.rb  
@@ -134,6 +134,8 @@ module Math  
else  
Complex(x, -y)  
end

- elsif a.respond\_to?(:nan?) and a.nan?
- 

```
 a

```

elsif a \>= 0  
rsqrt(a)  
else

* * *

[http://redmine.ruby-lang.org/issues/show/913](http://redmine.ruby-lang.org/issues/show/913)

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<div class="post-metadata">

**Author:** ![Yuki\_S](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/a6a055/32.png) [@Yuki\_S](https://www.ruby-forum.com/u/Yuki_S)\
**Post date:** [December 22, 2008, 12:34pm UTC](https://www.ruby-forum.com/t/bug-913-mathn-b-7-l9g-bsqrt-nan-b-j-ag-t-k-j-k-b/156169/2 "2008-12-22T12:34:04Z")

</div>

e$B$1$$$8$e!w$$$7$D$+$G$9e(B.

In [ruby-dev :37537] the message: "[ruby-dev:37537] [Bug #913] mathn  
e$B$7$?\>l9g!"e(Bsqrt(NaN) e$B$,J#AG?t$K$J$ke(B ", on Dec/22 11:38(JST)  
Yuki S.  
writes:

> e$B%A%1%C%He(B #913 e$B$,99?7$5$l$^$7$?!#e(B (by Yuki S.)
> 
> e$B$?$V$s!"$3$s$J46$8$@$H;W$$$^$9!#%3%\_%C%H$7$F$h$$$G$9$+e(B? \< e$B@PDM$5$se(B

e$BCM$,JQ$@$H$$$&0UL#$G$Oe(B, e$B2?$i$+$NBP=h$,$"$k$Y$-$@$H;W$$$^$9e(B.  
e$B$,e(B

,  
basee$B$H$J$C$F$$$ke(BComplexe$B$N?6$kIq$$$K4p$E$$$F$$$k$N$Ge(B,e$B$^$:e(B,  
Complexe$B$Ke(B  
nane$B$r?)$o$;$?$H$-$N?6$kIq$$$rL@3N$K$7$?J}$,NI$$$N$G$Oe(B?

irb(main):001:0\> nan = 0.0/0  
=\> NaN  
irb(main):002:0\> Complex(nan,0)  
=\> (NaN+0i)  
irb(main):003:0\> Complex(0,nan)  
=\> (0+NaN\*i)

e$B$3$l$i$N?6$kIq$$$O$3$l$GNI$$$s$G$9$+$Me(B?

\_\_  
----------------------------------------------------\>\> e$B@PDMe(B  
e$B7=\<ye(B \<\<—  
----------------------------------\>\> e-mail: removed\_email\_address@domain.invalid \<\<—

---

<div class="post-metadata">

**Author:** ![Yuki\_S](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/a6a055/32.png) [@Yuki\_S](https://www.ruby-forum.com/u/Yuki_S)\
**Post date:** [December 22, 2008, 1:47pm UTC](https://www.ruby-forum.com/t/bug-913-mathn-b-7-l9g-bsqrt-nan-b-j-ag-t-k-j-k-b/156169/3 "2008-12-22T13:47:22Z")

</div>

> > e$B$?$V$s!"$3$s$J46$8$@$H;W$$$^$9!#%3%\_%C%H$7$F$h$$$G$9$+e(B? \< e$B@PDM$5$se(B
> 
> e$BCM$,JQ$@$H$$$&0UL#$G$Oe(B, e$B2?$i$+$NBP=h$,$"$k$Y$-$@$H;W$$$^$9e(B. e$B$,e(B
> 
> , basee$B$H$J$C$F$$$ke(BComplexe$B$N?6$kIq$$$K4p$E$$$F$$$k$N$Ge(B,e$B$^$:e(B, Complexe$B$Ke(B  
> nane$B$r?)$o$;$?$H$-$N?6$kIq$$$rL@3N$K$7$?J}$,NI$$$N$G$Oe(B?

e$B$"$^$j4X78$J$$$h$&$J5$$,$7$^$9!#e(Bmatnn e$B$J$7$G!"e(B

Math.sqrt(NaN) #=\> NaN

e$B$H$J$k$H$$$&$3$H$J$N$G!#e(B

> irb(main):001:0\> nan = 0.0/0  
> =\> NaN  
> irb(main):002:0\> Complex(nan,0)  
> =\> (NaN+0i)  
> irb(main):003:0\> Complex(0,nan)  
> =\> (0+NaN\*i)
> 
> e$B$3$l$i$N?6$kIq$$$O$3$l$GNI$$$s$G$9$+$Me(B?

e$B$?$H$($P!"e(Br6rs e$B$G!"e(B+nan.0+0i e$B$de(B 0+nan.0i  
e$B$H=q$$$?\>l9g$HF1$8$G9=$o$J$$$He(B  
e$B;W$C$F$$$^$9!#e(Bpython e$B$G$bF1$8$G$9!#e(B

e$B4pK\E\*$Ke(B Complex e$B$NMWAG$Oe(B real  
e$B$G$"$l$P$$$$$H$$$&H=CG$G$9!#$@$+$i!“e(B  
BigDecimal e$B$d$”$k$$$OL$CN$N\<B?t$N\<BAu$G$b\<u$1F~$l$^$9!#e(B

---

<div class="post-metadata">

**Author:** ![Yuki\_S](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/a6a055/32.png) [@Yuki\_S](https://www.ruby-forum.com/u/Yuki_S)\
**Post date:** [December 23, 2008, 7:29am UTC](https://www.ruby-forum.com/t/bug-913-mathn-b-7-l9g-bsqrt-nan-b-j-ag-t-k-j-k-b/156169/4 "2008-12-23T07:29:46Z")

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e$B$1$$$8$e!w$$$7$D$+$G$9e(B.

e$B2\<5-N;2r$G$9e(B.

Yuguie$B$5$s%A%’%C%/%$%s$7$F$$$?$@$1$J$$$G$7$g$&$+e(B?

In [ruby-dev :37550] the message: "[ruby-dev:37550] Re: [Bug #913]  
mathn e$B$7$?\>l9g!"e(Bsqrt(NaN) e$B$,J#AG?t$K$J$ke(B ", on Dec/22  
21:38(JST)  
Tadayoshi F. writes:

> e$B$?$H$($P!"e(Br6rs e$B$G!"e(B+nan.0+0i e$B$de(B 0+nan.0i e$B$H=q$$$?\>l9g$HF1$8$G9=$o$J$$$He(B  
> e$B;W$C$F$$$^$9!#e(Bpython e$B$G$bF1$8$G$9!#e(B
> 
> e$B4pK\E\*$Ke(B Complex e$B$NMWAG$Oe(B real e$B$G$"$l$P$$$$$H$$$&H=CG$G$9!#$@$+$i!“e(B  
> BigDecimal e$B$d$”$k$$$OL$CN$N\<B?t$N\<BAu$G$b\<u$1F~$l$^$9!#e(B

\_\_  
----------------------------------------------------\>\> e$B@PDMe(B  
e$B7=\<ye(B \<\<—  
----------------------------------\>\> e-mail: removed\_email\_address@domain.invalid \<\<—