From: Rob Biedenharn <Rob@...>
Date: 2009-10-27T06:52:19+09:00
Subject: Re: RCR: regex + regex


On Oct 26, 2009, at 5:13 PM, Roger Pack wrote:

> Feedback on the following suggestion for ruby:
> by default allow for adding regex's
>
> i.e.
>>> /foo/ + /bar/
> => /foobar/
>
> Thoughts?
> -r
> --

irb> a=/foo/
=> /foo/
irb> b=/bar/
=> /bar/
irb> class Regexp
irb>   def +(other)
irb>     self.class.new(self.to_s + other.to_s)
irb>     end
irb>   end
=> nil
irb> a+b
=> /(?-mix:foo)(?-mix:bar)/

This is obviously too naive an implementation, but if we change a to / 
foo/i then I'd expect
"Foobar" =~ (a+b)
to be true (well, I mean 0, of course) and
"fooBar" =~ (a+b)
to be nil.

What might be the corresponding * or - behaviors? It seems like
	a * b
is closer to
	/(a)*(b)/
than anything else I could think of and that immediately implies:
	a + b
becomes:
	/(a)+(b)/
rather than just /(a)(b)/

The fact that + is a meaningful character in a Regexp makes a  
universal meaning for it as an operation *on* regexps a bit ambiguous.

-Rob

Rob Biedenharn		http://agileconsultingllc.com
Rob@AgileConsultingLLC.com