From: "Wolfgang Nádasi-Donner" <wonado@...>
Date: 2007-03-07T21:25:12+09:00
Subject: Re: Regexp backtracking issues in 1.8

Vasile Gaburici schrieb:
> Basically Ruby 1.8 fails to backtrack correctly a number of regular
> expressions. The simplest one is probably:
> 
> irb(main):036:0>  /a(ba|.)*?a/.match('axba')
> => nil
> 
> There is more to it, and since I had to write it down for my students,
> I'm just going to link to the gory details:
> http://www.cs.umd.edu/~gaburici/rubyre.html
> 

It is an Error in Ruby 1.8. In Ruby 1.9 (with Oniguruma) it works correct 
("ruby-445" is a special naming of myself for some experiments):

 >>>>> Example >>>>>

C:\Dokumente und Einstellungen\wolfgang\Desktop>type regexerr.rb
p "axba".match(/a(ba|.)*?a/)
C:\Dokumente und Einstellungen\wolfgang\Desktop>ruby -v
ruby 1.8.5 (2006-08-25) [i386-mswin32]

C:\Dokumente und Einstellungen\wolfgang\Desktop>ruby regexerr.rb
nil

C:\Dokumente und Einstellungen\wolfgang\Desktop>ruby-445 regexerr.rb
#<MatchData:0x2ac7ab8>

C:\Dokumente und Einstellungen\wolfgang\Desktop>ruby-445 -v
ruby 1.9.0 (2006-10-28) [i386-mingw32]

 >>>>> EoE >>>>>

Wolfgang Nádasi-Donner