From: Tanaka Akira <akr@...17n.org>
Date: 2002-03-29T17:10:44+09:00
Subject: [ruby-dev:16669] Re: [OniGuruma] nested repeat operator

In article <20020329022810.68F9E17@helium.ruby-lang.org>,
  "K.Kosako" <kosako@sofnec.co.jp> writes:

> $B:#$N;EMM$O!"(B?,*,+$B$N$I$l$+$N7+$jJV$7(B(greedy$B$G$"$C$F$b$J$/$F$b(B)$B$,(B
> $BO"B3$9$k$H$-$O%(%i!<$K$7$F$$$^$9!#(B
> $B;EMM$H$7$FJQ$G$"$l$PD>$7$^$9!#(B

$B$U$H;W$C$?$s$G$9$,!"(B

(?:a*)??

$B$H$$$&$N$O(B a*?, a* $B$N$I$A$i$G$b$J$$FH<+$N5sF0$rI=8=$9$k$b$N$G$"$k$h$&(B
$B$J5$$,$7$^$9!#(B

% print -l b ab aab | ruby -ne 'p [/\A((?:a*)??).?b/, /\A(a*?).?b/, /\A(a*).?b/].map {|re| re =~ $_; $1}'
["", "", ""]
["", "", "a"]
["aa", "a", "aa"]

$B$D$^$j!"(Ba $B$,(B n$B2s%^%C%A$9$k$H$-!"(B
  a*? $B$O(B 0, 1, ... 
  a* $B$O(B n, n-1, ...
  (?:a*)?? $B$O(B 0, n, n-1, ...
$B$H$$$&=gHV$G;n$9$N$G$O$J$$$@$m$&$+!"$H$$$&$3$H$G$9!#(B

$B$H$O$$$&$b$N$N!"$3$s$J$3$H$OC/$b5$$K$7$J$$$G$7$g$&$7!"O"B3$r5v$9$h$&$K(B
$B$9$Y$-$@$H$^$G$O$$$$$^$;$s$1$l$I!#(B
-- 
[$BEDCf(B $BE/(B][$B$?$J$+(B $B$"$-$i(B][Tanaka Akira]
$B!V$U$($m(B! $B$o$+$a$A$c$s:n@o$G$9$(C"=$B!W(B(Little Worker, $B7KM7@84](B)