From: Ian Macdonald <ian@...>
Date: 2007-02-15T00:17:37+09:00
Subject: Re: Puzzling regex behaviour

On Wed 14 Feb 2007 at 10:25:10 +0900, Rob Biedenharn wrote:

> I'm beginning to wonder if the original question is even accurate.   
> Doing nothing more than changing the encoding and re-saving the file  
> (where the value for foo was a cut-n-paste from the email), there  
> doesn't seem to be any discrpeancy between ruby and irb.  (This  
> output is from ruby 1.8.5, but 1.8.2 was the same)
> 
> rab:code/ruby $ file regexp_and_alnum_versus_w.rb
> regexp_and_alnum_versus_w.rb: ISO-8859 text
> rab:code/ruby $ cat regexp_and_alnum_versus_w.rb
> foo = "pr?f?r?es"
> alnum = /[^[:alnum:]]/
> dubya = /\W/
> 
> puts "foo\n  => #{foo.inspect}"
> [ alnum, dubya ].each do |re|
>   puts "foo =~ #{re}\n  => #{foo =~ re}"
> end
> rab:code/ruby $ ruby regexp_and_alnum_versus_w.rb
> foo
>   => "pr\351f\351r\351es"
> foo =~ (?-mix:[^[:alnum:]])
>   => 2

What is your locale? I strongly suspect it's either unset or set to C.
In those cases, I get the same results as you.

If you use en_US or nl_NL, you'll find (or at least, I find) that
'foo =~ /[^[:alnum:]]/' returns nil in irb and 2 from a stand-alone
script.

In fact, even irb returns a different value from the command line. This
is bizarre:

$ irb -f < foo2
foo = "pr�f�r�es"
"pr\351f\351r\351es"
foo =~ /[^[:alnum:]]/
2
foo =~ /\W/
2

$ irb
irb(main):001:0> foo = "pr�f�r�es"
=> "pr\351f\351r\351es"
irb(main):002:0> foo =~ /[^[:alnum:]]/
=> nil
irb(main):003:0> foo =~ /\W/
=> 2

As you can see, interactively irb returns nil for that first regex match.

Ian
-- 
Ian Macdonald               | The cost of living hasn't affected its
ian@caliban.org             | popularity. 
http://www.caliban.org/     | 
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