From: Martin DeMello <martindemello@...>
Date: 2010-07-14T19:48:09+09:00
Subject: Re: I have some questions about this modified String class

On Wed, Jul 14, 2010 at 3:26 PM, Abder-Rahman Ali
<abder.rahman.ali@gmail.com> wrote:
> I have the following script that I just have only slight changes in the
> hash from "Why's poignant guide to Ruby" book:
>
> http://pastie.org/private/ojmcfglofwloqemqmuhra

pasting it inline:

class String
  @@syllables = [{'P' => 'Px','G' => 'Gx','B' => 'Bx','S' => 'Sx','W'
=> 'Wx','O' => 'Ox'}, {'R' => 'Rx','C' => 'Cx'}]
  def name_significance
    parts = self.split('-') # 'self' returns the current object. And,
'split' here means splitting based on (-)
    syllables = @@syllables.dup
    signif = parts.collect do |p|
      syllables.shift[p]
    end
    signif.join( ' ' )
  end
end

Your problem is the call to syllables.shift - it removes one element
from syllables and returns it. But it does this once per hyphen, and
syllable only has two elements, so when you say

> puts "Abder-Rahman-is-my-name".name_significance

the first time through the loop, you have:

p = Abder
syllables.shift = {"P"=>"Px", "G"=>"Gx", "B"=>"Bx", "S"=>"Sx",
"W"=>"Wx", "O"=>"Ox"}
syllables.shift[p] =

the second time through you have:

p = Rahman
syllables.shift = {"R"=>"Rx", "C"=>"Cx"}
syllables.shift[p] =

the third time:
p = is
syllables.shift = nil
s.rb:10:in `block in name_significance': undefined method `[]' for
nil:NilClass (NoMethodError)

> 2- How can I use the @@syllables? Or, more specific, what is the use of
> @@syllables here while I conclude that the purpose of this modification
> to the class String is to remove '-'?
>
> 3- Why all that code if the purpose is removing '-', such that we ONLY
> need self.split( '-' ) in the body of name_significance here?

I have no idea what this code is intended to do :) What it does do is
take in a string like "P-C" and return "Px Cx".

Here's the code with print statements:

class String
  @@syllables = [{'P' => 'Px','G' => 'Gx','B' => 'Bx','S' => 'Sx','W'
=> 'Wx','O' => 'Ox'}, {'R' => 'Rx','C' => 'Cx'}]
  def name_significance
    parts = self.split('-') # 'self' returns the current object. And,
'split' here means splitting based on (-)
    syllables = @@syllables.dup
    signif = parts.collect do |p|
      s = syllables.shift
      puts "p = #{p}"
      puts "syllables.shift = #{s.inspect}"
      puts "syllables.shift[p] = #{s[p]}"
      s[p]
    end
    signif.join( ' ' )
  end
end

puts "P-C".name_significance

martin