From: Pit Capitain <pit@...>
Date: 2006-04-06T22:36:52+09:00
Subject: Re: String generalization

Peter Szinek schrieb:
> Hello all,
> 
> I am having the following problem: I have to implement a method
> which accepts a string and returns a  generalized form of the string.
> Some examples:
> 
> '12345' -> \d+
> 'ABCDE' -> [A-Z]+
> 'john.smith@my.super.server.rb' -> [a-z]+\.[a-z]+@([a-z]+\.)+[a-z]
> '123-45-678-90' -> (\d+-)+\d+
> 'item:' -> [a-z]+:
> 'Peter, SZINEK': -> [A-Z][a-z]+, [A-Z]+
> 'http://www.google.com' -> [a-z]+://([a-z]+\.)+[a-z]
> 'jd�;d:L348kddd3' -> .*

Peter, thanks for the quiz. I needed it right now :-)

I'm not sure I understand the rules. I had expected:

   '//' -> /+
   'jd�;d:L348kddd3' -> [a-z]+�;[a-z]:[A-Z]\d+[a-z]+\d

Anyway, here's a first implementation for the use cases you've shown:

   def generalize( str )
     str.gsub( /\d+|[a-z]+|[A-Z]+|\./ ) do |match|
       case match
       when /\d{2,}/: "\\d+"
       when /\d/: "\\d"
       when /[a-z]{2,}/: "[a-z]+"
       when /[a-z]/: "[a-z]"
       when /[A-Z]{2,}/: "[A-Z]+"
       when /[A-Z]/: "[A-Z]"
       when /\./: "\\."
       end
     end.gsub( /(.+)\1+/, "(\\1)+" )
   end

You notice some repetitions, so you can generalize it further. It isn't 
perfect, but maybe gets you going.

Regards,
Pit