# Array#shuffle! returns nil?

**URL:** <https://www.ruby-forum.com/t/array-shuffle-returns-nil/140034>\
**Category:** Development\
**Created:** [June 10, 2008, 8:36am UTC](https://www.ruby-forum.com/t/array-shuffle-returns-nil/140034 "2008-06-10T08:36:29Z")\
**Posts on this page:** 5\
**Page:** 1

<div class="post-metadata">

**Author:** ![okkez](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/o/8edcca/32.png) [@okkez](https://www.ruby-forum.com/u/okkez)\
**Post date:** [June 10, 2008, 8:36am UTC](https://www.ruby-forum.com/t/array-shuffle-returns-nil/140034/1 "2008-06-10T08:36:29Z")

</div>

okkez e$B$G$9!#e(B

Array#shuffle! e$B$O$I$&$$$&\>l9g$Ke(B nil e$B$rJV$9$N$G$7$g$&$+!)e(B  
e$B$=$l$H$be(B RDoc e$B$,4V0c$C$F$$$k$N$G$7$g$&$+!)e(B

e$B%j%U%!%l%s%9%^%K%e%"%k$K%5%s%W%k$r=q$-$?$$$N$G!"e(B  
e$B65$($F$$$?$@$1$k$H=u$+$j$^$9!#e(B

$ ruby -v  
ruby 1.8.7 (2008-06-09 patchlevel 17) [i686-linux]

---

<div class="post-metadata">

**Author:** ![okkez](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/o/8edcca/32.png) [@okkez](https://www.ruby-forum.com/u/okkez)\
**Post date:** [June 10, 2008, 8:58am UTC](https://www.ruby-forum.com/t/array-shuffle-returns-nil/140034/2 "2008-06-10T08:58:10Z")

</div>

e$B$^$D$b$He(B e$B$f$-$R$m$G$9e(B

In message “Re: [ruby-dev:35034] Array#shuffle! returns nil ?”  
on Tue, 10 Jun 2008 14:00:56 +0900, okkez [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
writes:

|Array#shuffle! e$B$O$I$&$$$&\>l9g$Ke(B nil e$B$rJV$9$N$G$7$g$&$+!)e(B  
|e$B$=$l$H$be(B RDoc e$B$,4V0c$C$F$$$k$N$G$7$g$&$+!)e(B

nile$B$OJV$7$^$;$s$M!#!Ve(B!e$B7O$OJQ99$,$J$+$C$?;~$Ke(Bnile$B$rJV$9!W$H$$e(B  
e$B$&86B’$,$"$j$^$9$,!“e(Bshufflee$B$O!VJQ99$,$J$$!W$3$H$,$”$j$($J$$e(B  
e$B$N$G\>o$Ke(Bselfe$B$rJV$7$^$9!#$3$l$Oe(Breversee$B$K$b8@$($k$3$H$G$9!#e(B

---

<div class="post-metadata">

**Author:** ![okkez](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/o/8edcca/32.png) [@okkez](https://www.ruby-forum.com/u/okkez)\
**Post date:** [June 10, 2008, 10:44am UTC](https://www.ruby-forum.com/t/array-shuffle-returns-nil/140034/3 "2008-06-10T10:44:32Z")

</div>

e$B\>.GH$G$9!#e(B

> e$B$^$D$b$He(B e$B$f$-$R$m$G$9e(B

> |Array#shuffle! e$B$O$I$&$$$&\>l9g$Ke(B nil e$B$rJV$9$N$G$7$g$&$+!)e(B  
> |e$B$=$l$H$be(B RDoc e$B$,4V0c$C$F$$$k$N$G$7$g$&$+!)e(B
> 
> nile$B$OJV$7$^$;$s$M!#!Ve(B!e$B7O$OJQ99$,$J$+$C$?;~$Ke(Bnile$B$rJV$9!W$H$$e(B  
> e$B$&86B’$,$"$j$^$9$,!“e(Bshufflee$B$O!VJQ99$,$J$$!W$3$H$,$”$j$($J$$e(B  
> e$B$N$G\>o$Ke(Bselfe$B$rJV$7$^$9!#$3$l$Oe(Breversee$B$K$b8@$($k$3$H$G$9!#e(B

e$B$k$j$^$N$?$a$Ke(B shuffle!  
e$B$N2r@b$rF|K\8l$KLu$7$?$N$O;d$G$9$,!$$Ie(B  
e$B$&$$$&\>r7o$Ge(B nil  
e$B$,JV$5$l$k$N$+$h$/J,$+$i$J$$$^$^%(%i!\<$r7Q\>5e(B  
e$B$7$F$7$^$$$^$7$?!#XPXC!\*e(B

e$BJY6/$N$?$a$K$_J9$-$7$F$_$-$?$$$N$G$9$,!$2\<$Ne(B array.c e$B$Ne(B  
rb\_ary\_shuffle\_bang(VALUE ary)e$B$N%3!\<%I$G!$e(Breturn ary;  
e$B$7$+$J$$$H$$$&$3$H$+$i!$\>e5-$NH=CG$O$G$-$k$N$G$7$g$&$+!#e(B  
call-seq: e$B$N$[$&$O4V0c$C$F$$$k$o$1$G$9$,!#e(B

e$B$"$H!$e(Bnil e$B$,JV$k$N$Oe(B return Qnil;  
e$B$GH=CG$G$-$k$H$$$&$3$He(B  
e$B$G$h$$$N$G$7$g$&$+!#e(B

/\*

- call-seq:
- 

```
array.shuffle! -> array or nil

```

- 
- Shuffles elements in _self_ in place.  
\*/

static VALUE  
rb\_ary\_shuffle\_bang(VALUE ary)  
{  
long i = RARRAY\_LEN(ary);

```
rb_ary_modify(ary);
while (i) {

```

long j = rb\_genrand\_real()\*i;  
VALUE tmp = RARRAY\_PTR(ary)[–i];  
RARRAY\_PTR(ary)[i] = RARRAY\_PTR(ary)[j];  
RARRAY\_PTR(ary)[j] = tmp;  
}  
return ary;  
}

---

<div class="post-metadata">

**Author:** ![okkez](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/o/8edcca/32.png) [@okkez](https://www.ruby-forum.com/u/okkez)\
**Post date:** [June 10, 2008, 10:45am UTC](https://www.ruby-forum.com/t/array-shuffle-returns-nil/140034/4 "2008-06-10T10:45:07Z")

</div>

e$B$^$D$b$He(B e$B$f$-$R$m$G$9e(B

In message “Re: [ruby-dev:35038] Re: Array#shuffle! returns nil ?”  
on Tue, 10 Jun 2008 16:58:25 +0900, “Hideo Konami”  
[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) writes:

|e$B$k$j$^$N$?$a$Ke(B shuffle! e$B$N2r@b$rF|K\8l$KLu$7$?$N$O;d$G$9$,!$$Ie(B  
|e$B$&$$$&\>r7o$Ge(B nil e$B$,JV$5$l$k$N$+$h$/J,$+$i$J$$$^$^%(%i!\<$r7Q\>5e(B  
|e$B$7$F$7$^$$$^$7$?!#XPXC!\*e(B

e$B$$$($$$(!"85$,4V0c$C$F$k$N$$$1$J$$$o$1$G!#e(B

|e$BJY6/$N$?$a$K$_J9$-$7$F$_$-$?$$$N$G$9$,!$2\<$Ne(B array.c e$B$Ne(B  
|rb\_ary\_shuffle\_bang(VALUE ary)e$B$N%3!\<%I$G!$e(Breturn ary;  
|e$B$7$+$J$$$H$$$&$3$H$+$i!$\>e5-$NH=CG$O$G$-$k$N$G$7$g$&$+!#e(B  
|call-seq: e$B$N$[$&$O4V0c$C$F$$$k$o$1$G$9$,!#e(B

Ce$B$G$9$+$i!"e(Breturne$B$7$J$$$H$3$m$+$iCM$,JQ$($k$3$H$,$J$$$N$OL@e(B  
e$B$i$+$G!"e(B

- return arye$B$7$+$J$$e(B
- ary(e$BBh0l0z?te(B)e$B$Oe(Bselfe$B$@$+$ie(Bnile$B$G$O$"$j$($J$$e(B
- e$B4X?tCf$Ge(Barye$B$r=q$-49$($F$$$J$$e(B

e$B$3$H$+$ie(Bnile$B$,JV$i$J$$$3$H$rH=CG$G$-$^$9!#e(B

|e$B$"$H!$e(Bnil e$B$,JV$k$N$Oe(B return Qnil; e$B$GH=CG$G$-$k$H$$$&$3$He(B  
|e$B$G$h$$$N$G$7$g$&$+!#e(B

return Qnil;e$B$,9T$o$l$F$$$l$P3N\<B$G$9$,!“$=$NB\>e(Breturne$B$G;XDj$5e(B  
e$B$l$?$b$N$,e(Bnile$B$G$J$$$+$H$&$+3NG’$9$kI,MW$O$”$j$^$9!#e(B

```
                            e$B$^$D$b$He(B e$B$f$-$R$me(B /:|)

```

---

<div class="post-metadata">

**Author:** ![okkez](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/o/8edcca/32.png) [@okkez](https://www.ruby-forum.com/u/okkez)\
**Post date:** [June 12, 2008, 1:15pm UTC](https://www.ruby-forum.com/t/array-shuffle-returns-nil/140034/5 "2008-06-12T13:15:53Z")

</div>

okkez e$B$G$9!#e(B

2008/06/10 15:20 Yukihiro M. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid):

> e$B$N$G\>o$Ke(Bselfe$B$rJV$7$^$9!#$3$l$Oe(Breversee$B$K$b8@$($k$3$H$G$9!#e(B

e$B@bL@$"$j$,$H$&$4$6$$$^$9!#e(B

# e$B$b$&$A$g$C$H$A$c$s$He(BCe$B$N%3!\<%IFI$a$k$h$&$K$J$j$?$$!#!#!#e(B