From: Wesley J Landaker <wjl@...>
Date: 2003-05-31T03:26:53+09:00
Subject: regexp operators

Hi folks,

In doing some work with parsers the other day, I ended up with a 
situation where I wanted to embed and combine regexps easily, 
perserving any flags that they may have on them (such as 
case-sensitivity, etc).

So I whipped this out really quick. It lets you combine regexp by adding 
them (+), ORing them (|) or by including them /blah#{some_regexp}blah/ 
inside each other, while preserving all flags. (At least, all flags 
that can be preserved--I can't do anything about the encodings if they 
mismatch... but I use all UTF-8 regexps, so I always use 'u'). This 
could potentially be extended to support other operations--but I 
haven't needed them yet on the project I'm tinkering with.

Maybe this is useful or interesting to somebody besides me. ;)

class Regexp
  @@inspect_regex = %r{/(.*)/((?:m|i|x)*)}

  def options
    return @@inspect_regex.match(self.inspect)[2]
  end

  def to_s
    self.inspect =~ @@inspect_regex
    if $2.length > 0
      "(?#{$2}:#{$1})"
    else
      "(?:#{$1})"
    end
  end

  def |(other)
    /#{self}|#{other}/u
  end

  def +(other)
    /#{self}#{other}/u
  end
end

Super simple, but has been endlessly handy for me:

$ irb
irb(main):001:0> require 'RegexpOps'
=> true
irb(main):002:0> /bar/ + /foo/
=> /(?:bar)(?:foo)/u
irb(main):003:0> /bar/i + /foo/
=> /(?i:bar)(?:foo)/u
irb(main):004:0> /bar/i + /foo/m
=> /(?i:bar)(?m:foo)/u
irb(main):005:0> /bar/ix + /foo/m
=> /(?ix:bar)(?m:foo)/u
irb(main):006:0> baz = /bar/i + /foo/
=> /(?i:bar)(?:foo)/u
irb(main):007:0> %r!foo#{/bar/i}*#{baz}?!
=> /foo(?i:bar)*(?:(?i:bar)(?:foo))?/
irb(main):008:0> /test/mi.options
=> "mi"

And stuff like that. =)

-- 
Wesley J. Landaker - wjl@icecavern.net
OpenPGP FP: C99E DF40 54F6 B625 FD48  B509 A3DE 8D79 541F F830