From: ara.t.howard@...
Date: 2006-07-13T04:31:46+09:00
Subject: Re: Help with a regexp

On Thu, 13 Jul 2006 dblack@wobblini.net wrote:

> Hi --
>
> On Thu, 13 Jul 2006, Daniel Schierbeck wrote:
>
>> My problem is that I have a string like this: "3:foo6:monkey5:sheep", which 
>> I need to separate into ["foo", "monkey", "sheep"]. The values can contain 
>> numeric values, so splitting at \d won't work. This is what makes it 
>> difficult:
>> 
>>  "3:ab23:cat5:sheep" => ["ab2", "cat", "sheep"]
>> 
>> I need to grab the number, then read that many characters, then read the 
>> next number, etc.
>
> How do you know, in the case of:
>
>  2:ab23:cat
>
> which of the two is invalid?

the second.  it's invalid here

   2:ab23:cat
             ^
             ^

virtual position 10.


     harp:~ > cat a.rb
     require 'strscan'

     class List < ::Array
       def initialize s
         parse s
       end
       class ParseError < ::StandardError; end
       def parse s
         clear
         ss = StringScanner.new s.to_s
         until ss.eos?
           n = ss.scan %r/^\d+:/
           raise ParseError, "syntax error beginning @ pos <#{ ss.pos }>" unless n

           n = n.to_i
           raise RangeError, "bad length <#{ n }>" if n < 0

           word = ss.scan(%r/.{0,#{ n }}/).to_s

           raise ParseError, "syntax error beginning @ pos <#{ ss.pos }>" unless
             word.size == n

           self << word
         end
       end
     end

     list = List.new "3:ab23:cat5:sheep"
     p list

     list = List.new "2:ab23:cat"
     p list

     harp:~ > ruby a.rb
     ["ab2", "cat", "sheep"]
     a.rb:20:in `parse': syntax error beginning @ pos <10> (List::ParseError)
             from a.rb:5:in `initialize'
             from a.rb:31


regards.

-a
-- 
suffering increases your inner strength.  also, the wishing for suffering
makes the suffering disappear.
- h.h. the 14th dali lama