# /(.)(.)/.match("ab").select {|v| true } is empty

**URL:** <https://www.ruby-forum.com/t/match-ab-select-v-true-is-empty/136365>\
**Category:** Development\
**Created:** [May 1, 2008, 9:21am UTC](https://www.ruby-forum.com/t/match-ab-select-v-true-is-empty/136365 "2008-05-01T09:21:58Z")\
**Posts on this page:** 5\
**Page:** 1

<div class="post-metadata">

**Author:** ![Tanaka\_A](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/c67d28/32.png) [@Tanaka\_A](https://www.ruby-forum.com/u/Tanaka_A)\
**Post date:** [May 1, 2008, 9:21am UTC](https://www.ruby-forum.com/t/match-ab-select-v-true-is-empty/136365/1 "2008-05-01T09:21:58Z")

</div>

e$B0J2\<$N$h$&$K!"e(BMatchData#select e$B$G%V%m%C%/$,\>o$K??$J$N$K7k2Le(B  
e$B$,6u$K$J$k$N$OJQ$G$O$J$$$G$7$g$&$+!#e(B

% ./ruby -ve ‘p(/(.)(.)/.match(“ab”).select {|v| true })’  
ruby 1.9.0 (2008-05-01 revision 16250) [i686-linux]  
[]

e$B%^%K%e%"%k$K$Oe(B self.to\_a.select { … } e$B$HF1$8$H=q$$$F$"$j$^e(B  
e$B$9$,!"$=$&$9$k$H6u$G$O$J$/$J$j$^$9!#e(B

% ./ruby -ve ‘p(/(.)(.)/.match(“ab”).to\_a.select {|v| true })’  
ruby 1.9.0 (2008-05-01 revision 16250) [i686-linux]  
[“ab”, “a”, “b”]

---

<div class="post-metadata">

**Author:** ![Tanaka\_A](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/c67d28/32.png) [@Tanaka\_A](https://www.ruby-forum.com/u/Tanaka_A)\
**Post date:** [May 1, 2008, 2:24pm UTC](https://www.ruby-forum.com/t/match-ab-select-v-true-is-empty/136365/2 "2008-05-01T14:24:53Z")

</div>

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

In message “Re: [ruby-dev:34556] /(.)(.)/.match(“ab”).select {|v| true }  
is empty”  
on Thu, 1 May 2008 16:20:53 +0900, Tanaka A. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
writes:

|e$B0J2\<$N$h$&$K!"e(BMatchData#select e$B$G%V%m%C%/$,\>o$K??$J$N$K7k2Le(B  
|e$B$,6u$K$J$k$N$OJQ$G$O$J$$$G$7$g$&$+!#e(B

MatchData#selecte$B$Oe(Bvalues\_ate$B$Ne(Baliase$B$G$9$+$ie(BEnumerablee$B7O$Ne(B  
selecte$B$H$O5sF0$,0[$J$j$^$9!#La$jCM$O;XDj$7$?0z?t$r%$%s%G%C%/e(B  
e$B%9$H$9$kCM$rMWAG$H$9$kG[Ns$G$9!#e(BRDoce$B$K$O0J2\<$N$h$&$K$"$j$^$9!#e(B

```
 mtch.values_at([index]*) => array
 mtch.select([index]*) => array

```

Uses each _index_ to access the matching values, returning an  
array of  
the corresponding matches.

```
 m = /(.)(.)(\d+)(\d)/.match("THX1138: The Movie")
 m.to_a #=> ["HX1138", "H", "X", "113", "8"]
 m.values_at(0, 2, -2) #=> ["HX1138", "X", "113"]

```

|e$B%^%K%e%“%k$K$Oe(B self.to\_a.select { … } e$B$HF1$8$H=q$$$F$”$j$^e(B  
|e$B$9$,!"$=$&$9$k$H6u$G$O$J$/$J$j$^$9!#e(B

e$B$G$9$+$i!“$3$l$O!V%^%K%e%”%k!W$N4V0c$$$@$H;W$$$^$9!#D{@5$7$?e(B  
e$BJ}$,$h$$$G$7$g$&$M!#e(B

e$B$=$l$O$=$l$H$7$F!"e(Bselecte$B$H$$$&L\>A0$O8m2r$r@8$\_$d$9$$$N$G!"e(B

- e$B:o=|e(B or e$B2~L\>$9$ke(B
- e$B0z?t$,L5$$e(B and/or e$B%V%m%C%/$,M?$($i$l$F$$$k\>l9g$K$O@Q6KE\*e(B  
e$B$K%(%i!\<$^$?$O7Y9p$K$9$k!#e(B

e$B$J$I$NBP:v$r$9$k$3$H$ONI$$$3$H$@$H;W$$$^$9!#e(B

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

```

---

<div class="post-metadata">

**Author:** ![Tanaka\_A](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/c67d28/32.png) [@Tanaka\_A](https://www.ruby-forum.com/u/Tanaka_A)\
**Post date:** [May 1, 2008, 2:54pm UTC](https://www.ruby-forum.com/t/match-ab-select-v-true-is-empty/136365/3 "2008-05-01T14:54:56Z")

</div>

In article [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid),  
Yukihiro M. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) writes:

> MatchData#selecte$B$Oe(Bvalues\_ate$B$Ne(Baliase$B$G$9$+$ie(BEnumerablee$B7O$Ne(B  
> selecte$B$H$O5sF0$,0[$J$j$^$9!#La$jCM$O;XDj$7$?0z?t$r%$%s%G%C%/e(B  
> e$B%9$H$9$kCM$rMWAG$H$9$kG[Ns$G$9!#e(BRDoce$B$K$O0J2\<$N$h$&$K$"$j$^$9!#e(B

e$B$\*$)!"e(Brdoc e$B$OFI$s$G$^$;$s$G$7$?!#e(B

e$B$7$+$7!“$=$N@bL@$Oe(B 1.8.1 e$B$+$ie(B 1.8.6  
e$B$^$G$N5sF0$H$”$C$F$$$^$;$s!#e(B

% ruby-1.8.6 -ve ‘p(/(.)(.)(\d+)(\d)/.match(“THX1138: The  
Movie”).select(0, 2, -2))’  
ruby 1.8.6 (2007-03-13 patchlevel 0) [i686-linux]  
-e:1:in `select’: wrong number of arguments (3 for 0) (ArgumentError)  
from -e:1

% ruby-1.8.6 -ve ‘p(/(.)(.)(\d+)(\d)/.match(“THX1138: The Movie”).select  
{ true })’  
ruby 1.8.6 (2007-03-13 patchlevel 0) [i686-linux]  
[“HX1138”, “H”, “X”, “113”, “8”]

e$B@bL@$,$D$$$?$N$Oe(B 1.8.2 e$B$G$9$,!“$=$NCJ3,$G\<B:]$N5sF0$H@bL@$Ke(B  
e$B?)$$0c$$$,$”$j$^$9!#e(B

e$B@bL@$O$^$D$b$H$5$s$N$$$&$h$&$Ke(B values\_at e$B$G$9$,!"\<BAu$Oe(B  
Enumerable e$BE\*$J$b$N$G$9!#e(B

e$B$=$7$F!"e(B1.8.0 e$B$Oe(B values\_at e$B$He(B Enumerable  
e$BE\*$J$b$N$,:.$6$C$Fe(B  
e$B$$$F!"e(Bvalues\_at e$B$N$[$&$Oe(B values\_at  
e$B\<+BN$r;H$($H$$$&7Y9p$,=Pe(B  
e$B$^$9!#e(B

% ruby-1.8.0 -ve ‘p(/(.)(.)(\d+)(\d)/.match(“THX1138: The  
Movie”).select(0, 2, -2))’  
ruby 1.8.0 (2003-08-04) [i686-linux]  
-e:1: warning: MatchData#select(index…) is deprecated; use  
MatchData#values\_at  
[“HX1138”, “X”, “113”]

% ruby-1.8.0 -ve ‘p(/(.)(.)(\d+)(\d)/.match(“THX1138: The Movie”).select  
{ true })’  
ruby 1.8.0 (2003-08-04) [i686-linux]  
[“HX1138”, “H”, “X”, “113”, “8”]

e$B$3$l$r$\_$k$H!“$`$7$me(B rdoc  
e$B$K$h$k@bL@$,4V0c$C$F$$$F!”$=$N4V0c$Ce(B  
e$B$?@bL@$Ke(B 1.9 e$B$,=\>$C$F$7$^$C$?$H;W$($k$N$G$9$,$I$&$G$7$g$&$+e(B?

(e$B$=$7$F!"e(B1.8.7 e$B$K$=$l$,e(B backport  
e$B$5$l$FHs8\_49@-$,H/@8$7$F$\*e(B  
e$B$j!"e(Brubyspec e$B$G8!=P$5$l$k$N$G$9$,!#e(B)

---

<div class="post-metadata">

**Author:** ![Tanaka\_A](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/c67d28/32.png) [@Tanaka\_A](https://www.ruby-forum.com/u/Tanaka_A)\
**Post date:** [May 1, 2008, 4:06pm UTC](https://www.ruby-forum.com/t/match-ab-select-v-true-is-empty/136365/4 "2008-05-01T16:06:13Z")

</div>

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

In message “Re: [ruby-dev:34562] Re: /(.)(.)/.match(“ab”).select {|v|  
true } is empty”  
on Thu, 1 May 2008 21:54:15 +0900, Tanaka A. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
writes:

|\> MatchData#selecte$B$Oe(Bvalues\_ate$B$Ne(Baliase$B$G$9$+$ie(BEnumerablee$B7O$Ne(B  
|\> selecte$B$H$O5sF0$,0[$J$j$^$9!#La$jCM$O;XDj$7$?0z?t$r%$%s%G%C%/e(B  
|\> e$B%9$H$9$kCM$rMWAG$H$9$kG[Ns$G$9!#e(BRDoce$B$K$O0J2\<$N$h$&$K$“$j$^$9!#e(B  
|  
|e$B$\*$)!“e(Brdoc e$B$OFI$s$G$^$;$s$G$7$?!#e(B  
|  
|e$B$7$+$7!”$=$N@bL@$Oe(B 1.8.1 e$B$+$ie(B 1.8.6 e$B$^$G$N5sF0$H$”$C$F$$$^$;$s!#e(B  
|  
|% ruby-1.8.6 -ve ‘p(/(.)(.)(\d+)(\d)/.match(“THX1138: The Movie”).select(0, 2, -2))’  
|ruby 1.8.6 (2007-03-13 patchlevel 0) [i686-linux]  
|-e:1:in `select’: wrong number of arguments (3 for 0) (ArgumentError)  
| from -e:1  
|  
|% ruby-1.8.6 -ve ‘p(/(.)(.)(\d+)(\d)/.match(“THX1138: The Movie”).select { true })’  
|ruby 1.8.6 (2007-03-13 patchlevel 0) [i686-linux]  
|[“HX1138”, “H”, “X”, “113”, “8”]

1.8e$B$G$Oe(BMatchData#selecte$B$O!“%V%m%C%/$,M?$($i$l$?$ie(BEnumerablee$B7O!“e(B  
e$B0z?t$,M?$($i$l$?$ie(Bvalues\_ate$B$H$$$&F0$-$r$7$F$$$^$7$?!#$,!”:.$8e(B  
e$B$k$N$ONI$/$J$$$@$m$&$H;W$C$?3P$($O$”$j$^$9!#e(B

e$B$G!"e(BMatchDatae$B$Oe(BEnumerablee$B$re(Bincludee$B$7$F$$$J$$$7!"e(Bselecte$B$@$1e(B  
Enumerablee$B7O$NF0$-$r$7$F$b$7$g$&$,$J$$$@$m$&$H;W$C$Fe(B1.9e$B$r8=e(B  
e$B:_$N$h$&$K$7$?$h$&$J5$$,$7$^$9$,!"e(B1.8e$B$G$OJ,N%$9$kJ}8~$K?J2=e(B  
e$B$7$F$?$_$?$$$G$9$M$'!#F1$8?M$,:n6H$7$?$H$O;W$($J$$;YN%LGNv$5!#e(B  
e$BH?\>J$G$9!#e(B

|e$B$3$l$r$\_$k$H!“$`$7$me(B rdoc e$B$K$h$k@bL@$,4V0c$C$F$$$F!”$=$N4V0c$Ce(B  
|e$B$?@bL@$Ke(B 1.9 e$B$,=\>$C$F$7$^$C$?$H;W$($k$N$G$9$,$I$&$G$7$g$&$+e(B?

e$B$H$$$&$+!"e(B1.8e$B$He(B1.9e$B$H$G0c$&;~E@$G0[$J$kH=CG$r$7$F$7$^$C$?$H$$e(B  
e$B$&$3$H$N$h$&$G$9!#$4$a$s$J$5$$!#e(B

|(e$B$=$7$F!"e(B1.8.7 e$B$K$=$l$,e(B backport e$B$5$l$FHs8\_49@-$,H/@8$7$F$\*e(B  
|e$B$j!"e(Brubyspec e$B$G8!=P$5$l$k$N$G$9$,!#e(B)

1.8e$B$NHO0OFb$G=EBg$JHs8\_49@-$rH/@8$5$;$k$N$OK\0U$G$O$J$$$N$G!“e(B  
e$B$$$^$5$i$G$9$,e(B1.8.7e$B$Ne(BMatchData#selecte$B$Oe(B1.8.6e$B$HF1$8$h$&$Ke(B  
Enumerablee$B7O$NF0:n$KLa$9e(B(RDoce$B$b$=$l$K$”$o$;$F=q$-49$($ke(B)e$B$Y$-e(B  
e$B$G$7$g$&!#e(B

e$B$G!“e(B1.9e$B$G$I$&$9$k$+$G$9$,!“e(BMatchDatae$B$KBP$7$Fe(BEnumerablee$B7O$Ne(B  
select(e$B$@$1e(B)e$B$,I,MW$K$J$k6ILL$O$[$H$s$I$J$$$H;W$$$^$9$7!”$H$Oe(B  
e$B$$$(e(Bselecte$B$H$$$&%a%=%C%I$r8+$k$HC/$b$,e(BEnumerablee$B7O$NF0:n$r4|e(B  
e$BBT$7$^$9$+$i!”$$$C$=:o=|$7$F$7$^$&$N$,$h$$$N$G$O$J$$$+$H;W$$e(B  
e$B$^$9!#e(B

e$B$I$&$G$7$g$&!)e(B

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

```

---

<div class="post-metadata">

**Author:** ![Tanaka\_A](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/c67d28/32.png) [@Tanaka\_A](https://www.ruby-forum.com/u/Tanaka_A)\
**Post date:** [May 1, 2008, 5:32pm UTC](https://www.ruby-forum.com/t/match-ab-select-v-true-is-empty/136365/5 "2008-05-01T17:32:11Z")

</div>

In article [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid),  
Yukihiro M. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) writes:

> 1.8e$B$G$Oe(BMatchData#selecte$B$O!"%V%m%C%/$,M?$($i$l$?$ie(BEnumerablee$B7O!"e(B  
> e$B0z?t$,M?$($i$l$?$ie(Bvalues\_ate$B$H$$$&F0$-$r$7$F$$$^$7$?!#e(B

e$B$=$&$$$&F0$-$r$7$F$$$?$N$Oe(B 1.8.0 e$B$@$1$G$9!#e(B

> e$B$,!“:.$8e(B  
> e$B$k$N$ONI$/$J$$$@$m$&$H;W$C$?3P$($O$”$j$^$9!#e(B

e$B$=$N;W$$$Oe(B 1.8.1 e$B$G\<B8=$5$l!"$=$l0J9\_$O0z?t$,M?$($i$l$k$H%(e(B  
e$B%i!\<$K$J$C$F$$$^$9!#e(B

> 1.8e$B$NHO0OFb$G=EBg$JHs8\_49@-$rH/@8$5$;$k$N$OK\0U$G$O$J$$$N$G!“e(B  
> e$B$$$^$5$i$G$9$,e(B1.8.7e$B$Ne(BMatchData#selecte$B$Oe(B1.8.6e$B$HF1$8$h$&$Ke(B  
> Enumerablee$B7O$NF0:n$KLa$9e(B(RDoce$B$b$=$l$K$”$o$;$F=q$-49$($ke(B)e$B$Y$-e(B  
> e$B$G$7$g$&!#e(B

e$B$=$&;W$$$^$9!#e(B

> e$B$G!“e(B1.9e$B$G$I$&$9$k$+$G$9$,!“e(BMatchDatae$B$KBP$7$Fe(BEnumerablee$B7O$Ne(B  
> select(e$B$@$1e(B)e$B$,I,MW$K$J$k6ILL$O$[$H$s$I$J$$$H;W$$$^$9$7!”$H$Oe(B  
> e$B$$$(e(Bselecte$B$H$$$&%a%=%C%I$r8+$k$HC/$b$,e(BEnumerablee$B7O$NF0:n$r4|e(B  
> e$BBT$7$^$9$+$i!”$$$C$=:o=|$7$F$7$^$&$N$,$h$$$N$G$O$J$$$+$H;W$$e(B  
> e$B$^$9!#e(B
> 
> e$B$I$&$G$7$g$&!)e(B

[ruby-dev:15419] e$B$r8+$D$1$FFI$_$^$7$?$,!"M_$7$+$C$?$N$O7k6Ie(B  
select e$B$8$c$J$/$Fe(B values\_at  
e$B$@$C$?!"$C$F$$$&$3$H$J$s$G$9$+$M!#e(B

e$B:o=|$9$k$H$$$&$N$O!"e(BMatchData#select e$B$N:G=i$N0U?^$K1h$C$F$$e(B  
e$B$k$H$O$$$($k$s$8$c$J$$$G$7$g$&$+!#e(B