From: "Berger, Daniel" <djberge@...>
Date: 2002-09-25T23:41:11+09:00
Subject: RE: Regular expression object question


> At Wed, 25 Sep 2002 06:57:01 +0900,
> Joel VanderWerf wrote:
> 
> > irb(main):001:0> /ab/+"cd"
> > NameError: undefined method `+' for /ab/:Regexp
> >          from (irb):1
> > irb(main):002:0> class Regexp
> > irb(main):003:1>   def +(str)
> > irb(main):004:2>     Regexp.new(source + str)
> > irb(main):005:2>   end
> > irb(main):006:1> end
> > nil
> > irb(main):007:0> /ab/+"cd"
> > /abcd/
> > 
> > Seems reasonable. But then you would also want to test for a regex 
> > argument (and you can't just apply #to_s), and possibly 
> other arguments.
> > 
> > Is there a reason this doesn't already exist?
> 
> I don't know the reasons but I can imagine
> 
>   * Other #+ hardly raise but Regexp#+ does easily: /ab/ + "|"
> 
>   * source+Regexp::escape(str) is sefe but too rigid
> 
>   * Options wounld not be preserved: /<.*/m + ">" != /<.*>/m
> 
>   * Ruby 1.7 has Regexp#options but what is reasonable //mu + //nx
> 
>   * What should happen: "" + //

I wouldn't go out of my way to prevent people from shooting themselves in
the foot with pointless syntax like "" + // or /ab/ + "|".  My answer would
simply be, "don't do that".

As you mentioned, retaining options is a problem, since the source() method
doesn't retain that portion.  I'm not sure how you would deal with this in
1.6 (I haven't looked at this in 1.7).

/me thinks about this some more.

Regards,

Dan