From: Gavin Kistner <gavin@...>
Date: 2005-09-26T07:10:52+09:00
Subject: Re: String#ggsub

On Sep 25, 2005, at 3:33 PM, Logan Capaldo wrote:
>> I occasionally find myself with gsub regexp that either eat too  
>> much, or work within a nesting, such that I need to run gsub more  
>> than once in order to get the desired end result. The code I end  
>> up writing tends to be of the form:
>>
>> while foo.gsub!( /.../, ... ); end
>
> I'm kinda curious, can we see an example of a regex where this was  
> necessary?

Here's a pared-down example from this week's ruby quiz:

class Array; def random; self[ rand( self.length ) ]; end; end

class String
   def variation
     out = self.dup
     while out.gsub!( /\(([^())?]+)\)(\?)?/ ){
       ( $2 && ( rand > 0.5 ) ) ? '' : $1.split( '|' ).random
     }; end
     out
   end
end

q = "(How (much|many)|What) is (the (value|result) of)? 10 + 2?"
10.times{ puts q.variation }
#=> What is the value of 10 + 2?
#=> What is the value of 10 + 2?
#=> How many is  10 + 2?
#=> What is  10 + 2?
#=> What is  10 + 2?
#=> How many is  10 + 2?
#=> What is the value of 10 + 2?
#=> What is  10 + 2?
#=> What is the result of 10 + 2?
#=> What is the result of 10 + 2?