From: Charles Oliver Nutter <charles.nutter@...>
Date: 2009-02-05T07:53:55+09:00
Subject: [ruby-core:21839] Re: What does this regexp mean - /\c#{_J}/

Shri Borde wrote:
> I am combining the escaped control character syntax (\c/X/) with 
> variable interpolation (#{var_name}). It seems nonsensical, and its 
> probably only interesting for an academic interest (I am adding to the 
> RubySpecs). It does not seem to match anything at all. Its almost the 
> same output with both 1.8.6 and 1.9, but the warnings are given only in 
> 1.8.6.
> 
>  
> 
> Should it be a syntax error? Or can it actually match something?
> 
>  
> 
> irb(main):001:0> _J = "J"
> 
> => "J"
> 
> irb(main):002:0> re = /\c#{_J}/
> 
> (irb):2: warning: regexp has invalid interval
> 
> (irb):2: warning: regexp has `}' without escape

No warnings in JRuby but we appear to do the same thing. Parser artifact 
no doubt...I'd call it a bug.

- Charlie