# Tail call optimization

**URL:** <https://www.ruby-forum.com/t/tail-call-optimization/104648>\
**Category:** Development\
**Created:** [May 21, 2007, 7:24am UTC](https://www.ruby-forum.com/t/tail-call-optimization/104648 "2007-05-21T07:24:09Z")\
**Posts on this page:** 6\
**Page:** 1

<div class="post-metadata">

**Author:** ![SASADA\_Koichi](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/f1d935/32.png) [@SASADA\_Koichi](https://www.ruby-forum.com/u/SASADA_Koichi)\
**Post date:** [May 21, 2007, 7:24am UTC](https://www.ruby-forum.com/t/tail-call-optimization/104648/1 "2007-05-21T07:24:09Z")

</div>

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e$B$1$G$9!%e(B

def rec n  
rec n-1 if n \> 0  
end

rec 100000

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(1)  
e$B$3$l$Ge(BRubye$B$G$b4X?t7?%W%m%0%i%\_%s%0$,=PMh$k$\>!$$H$U$l$^$o$ke(B  
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(3) e$BCN$C$F$$$k?M$7$+;H$o$J$$$h$&$J!$1#$75!G=$K$9$ke(B  
e$B!!!Nc$($Pe(B ObjC e$B3HD%$de(B python like e$B%V%m%C%/$H$+$HF1$8e(B  
(3’) e$B$H$j$"$($:F~$l$F$\*$/$,!$$b$&$A$g$C$H!$;EMM$r8!F$$9$ke(B

e$B!!$A$J$\_$K!$$$$o$f$kKvHx:F5/$N:GE,2=!J\<+J,\<+?H$X$Ne(B jump  
e$B$KJQ49!K$G$O$Je(B  
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e$B$J$N$G!$9bB.2=$K$O$"$s$^$j4sM?$7$F$$$^$;$s!%e(B

---

<div class="post-metadata">

**Author:** ![SASADA\_Koichi](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/f1d935/32.png) [@SASADA\_Koichi](https://www.ruby-forum.com/u/SASADA_Koichi)\
**Post date:** [May 21, 2007, 3:13pm UTC](https://www.ruby-forum.com/t/tail-call-optimization/104648/2 "2007-05-21T15:13:58Z")

</div>

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

In message “Re: [ruby-dev:30800] tail call optimization”  
on Mon, 21 May 2007 14:23:38 +0900, SASADA Koichi [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
writes:

|(1) e$B$3$l$Ge(BRubye$B$G$b4X?t7?%W%m%0%i%\_%s%0$,=PMh$k$\>!$$H$U$l$^$o$ke(B  
|(2) Rubye$B$K9g$o$J$$$+$i5!G=$r$J$+$C$?;v$K$9$k!J\>C$9!Ke(B  
|(3) e$BCN$C$F$$$k?M$7$+;H$o$J$$$h$&$J!$1#$75!G=$K$9$ke(B  
|e$B!!!Nc$($Pe(B ObjC e$B3HD%$de(B python like e$B%V%m%C%/$H$+$HF1$8e(B  
|(3’) e$B$H$j$"$($:F~$l$F$\*$/$,!$$b$&$A$g$C$H!$;EMM$r8!F$$9$ke(B

(4) e$BF~$l$k$7;H$&$1$IJL$K?($l2s$k$3$H$^$G$O$7$J$$e(B

e$B$/$i$$$G$$$+$,$G$7$g$&!)e(B  
e$B;EMM$K$D$$$F$OLdBj$J$$$s$8$c$J$$$+$He(B  
e$B;W$$$^$9!#e(BRubye$B$N\>l9g!“e(Baliase$B$H$+$”$k$s$GK\Ev$K:F5"$J$N$+H=Dje(B  
e$B$9$k$N$K%3%9%H$,$+$+$j$^$9$+$i!"e(Bjumpe$B$X$N:GE,2=$O7k9=Fq$7$$$se(B  
e$B$G$J$$$+$H;W$$$^$9$7!#e(B

e$B$A$g$C$H9M$($?$N$O!"e(B recall e$B$H$$$&%-!\<%o!\<%I$rMQ0U$7$F!"e(B  
recall(args)e$B$G\<+J,\<+?H$r8F$S=P$7e(B(jumpe$B$K:GE,2=$G$-$ke(B)e$B$H$$$&$Ne(B  
e$B$O$I$&$G$7$g$&$M$(!#e(B

---

<div class="post-metadata">

**Author:** ![SASADA\_Koichi](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/f1d935/32.png) [@SASADA\_Koichi](https://www.ruby-forum.com/u/SASADA_Koichi)\
**Post date:** [May 21, 2007, 6:49pm UTC](https://www.ruby-forum.com/t/tail-call-optimization/104648/3 "2007-05-21T18:49:34Z")

</div>

e$B!!$5$5$@$G$9!%e(B

Yukihiro M. wrote:

> (4) e$BF~$l$k$7;H$&$1$IJL$K?($l2s$k$3$H$^$G$O$7$J$$e(B
> 
> e$B$/$i$$$G$$$+$,$G$7$g$&!)e(B e$B;EMM$K$D$$$F$OLdBj$J$$$s$8$c$J$$$+$He(B  
> e$B;W$$$^$9!#e(BRubye$B$N\>l9g!“e(Baliase$B$H$+$”$k$s$GK\Ev$K:F5"$J$N$+H=Dje(B  
> e$B$9$k$N$K%3%9%H$,$+$+$j$^$9$+$i!"e(Bjumpe$B$X$N:GE,2=$O7k9=Fq$7$$$se(B  
> e$B$G$J$$$+$H;W$$$^$9$7!#e(B

e$B!!$3$l$OKvHx:F5"$N:GE,2=$NOC$G$9$+!%e(BRubye$B$NJ8K!$r\<i$k8B$j!$%8%c%s%W$X$NJQe(B  
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e$B$k$N$J$i$J$s$H$G$b$J$j$=$&$G$9$,!%e(B

> e$B$A$g$C$H9M$($?$N$O!"e(B recall e$B$H$$$&%-!\<%o!\<%I$rMQ0U$7$F!"e(B  
> recall(args)e$B$G\<+J,\<+?H$r8F$S=P$7e(B(jumpe$B$K:GE,2=$G$-$ke(B)e$B$H$$$&$Ne(B  
> e$B$O$I$&$G$7$g$&$M$(!#e(B

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def cnt n  
retry n-1 if n\>0  
end

e$B!!$C$F!$%V%m%C%/Cf$G$O;H$($J$$$+$i%@%a$+!%e(B

---

<div class="post-metadata">

**Author:** ![SASADA\_Koichi](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/f1d935/32.png) [@SASADA\_Koichi](https://www.ruby-forum.com/u/SASADA_Koichi)\
**Post date:** [May 22, 2007, 5:38am UTC](https://www.ruby-forum.com/t/tail-call-optimization/104648/4 "2007-05-22T05:38:52Z")

</div>

e$B!!$5$5$@$G$9!%e(B

Yukihiro M. wrote:

> e$B$h$M!#F10U$7$^$9!#%a%=%C%I%k%C%/%"%C%W$r9T$C$F!"\<+J,\<+?H$r8Fe(B  
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> e$B%9%HE\*$K@^$j9g$o$J$$$G$7$g$&$M!#e(B

e$B!!$"$"!$@dBPL5M}$H8@$C$F$$$?$N$O%3%s%Q%$%k;~$Ke(B jump  
e$B$XCV$-49$($k!$$H$$$&e(B  
e$BOC$G$7$?!%e(B

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e$B$b!$%_%U$N$^$^$K$7$F$_$-$^$7$g$&$+!%e(B

---

<div class="post-metadata">

**Author:** ![SASADA\_Koichi](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/f1d935/32.png) [@SASADA\_Koichi](https://www.ruby-forum.com/u/SASADA_Koichi)\
**Post date:** [May 22, 2007, 3:30am UTC](https://www.ruby-forum.com/t/tail-call-optimization/104648/5 "2007-05-22T03:30:44Z")

</div>

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

In message “Re: [ruby-dev:30802] Re: tail call optimization”  
on Tue, 22 May 2007 01:48:34 +0900, SASADA Koichi [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
writes:

|\> e$B$/$i$$$G$$$+$,$G$7$g$&!)e(B e$B;EMM$K$D$$$F$OLdBj$J$$$s$8$c$J$$$+$He(B  
|\> e$B;W$$$^$9!#e(BRubye$B$N\>l9g!“e(Baliase$B$H$+$”$k$s$GK\Ev$K:F5"$J$N$+H=Dje(B  
|\> e$B$9$k$N$K%3%9%H$,$+$+$j$^$9$+$i!“e(Bjumpe$B$X$N:GE,2=$O7k9=Fq$7$$$se(B  
|\> e$B$G$J$$$+$H;W$$$^$9$7!#e(B  
|  
|e$B!!$3$l$OKvHx:F5”$N:GE,2=$NOC$G$9$+!%e(BRubye$B$NJ8K!$r\<i$k8B$j!$%8%c%s%W$X$NJQe(B  
|e$B49$O@dBP$KL5M}$J$s$8$c$J$$$+$H;W$$$^$9!%e(BJavae$B$G$$$&!$e(Bprivatee$B%a%=%C%I$r:ne(B  
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e$B%9%HE\*$K@^$j9g$o$J$$$G$7$g$&$M!#e(B

|\> e$B$A$g$C$H9M$($?$N$O!"e(B recall e$B$H$$$&%-!\<%o!\<%I$rMQ0U$7$F!"e(B  
|\> recall(args)e$B$G\<+J,\<+?H$r8F$S=P$7e(B(jumpe$B$K:GE,2=$G$-$ke(B)e$B$H$$$&$Ne(B  
|\> e$B$O$I$&$G$7$g$&$M$(!#e(B  
|  
|e$B!!$=$3$^$G$9$k$J$i%k!\<%W$G$$$$$h$&$J5$$O$7$^$9!%5$$N$;$$$+$7$i$s!%e(B

e$B$$$d!“:F5"8F=P$7$C$]$/8+$($k$N$,=EMW$J$N$G$7$g$&!”$?$V$s!#e(B  
recalle$B$O:G6aFI$s$@2?$+$N8@8l$K$D$$$F$?5!G=$G$9!#$(!\<$H!"e(BRe$B$@$Ce(B  
e$B$?$+$J!#e(B

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

```

---

<div class="post-metadata">

**Author:** ![SASADA\_Koichi](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/f1d935/32.png) [@SASADA\_Koichi](https://www.ruby-forum.com/u/SASADA_Koichi)\
**Post date:** [May 22, 2007, 7:55am UTC](https://www.ruby-forum.com/t/tail-call-optimization/104648/6 "2007-05-22T07:55:01Z")

</div>

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

In message “Re: [ruby-dev:30804] Re: tail call optimization”  
on Tue, 22 May 2007 12:38:05 +0900, SASADA Koichi [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
writes:

|e$B!!$G!$$3$l$O%G%U%)%k%H$G%_%U$K$7$F$$$^$9$,!$%_%s$K$7$H$-$^$9!)!!$=$l$He(B  
|e$B$b!$%_%U$N$^$^$K$7$F$_$-$^$7$g$&$+!%e(B

e$B%G%U%)%k%H%\*%s$G$$$$$s$8$c$J$$$G$7$g$&$+!#%9%?%C%/$N@aLs$Ke(B  
e$B$b$J$j$=$&$@$7!#e(B