From: ts <decoux@...>
Date: 2002-03-27T23:20:14+09:00
Subject: Re: Hash.new(Hash.new) doesn't use Hash.new as default value

>>>>> "J" == Jonas Delfs <jonas@NOSPAMdelfs.dk> writes:

J> If it's no bug, I think it's a bug in documentation. - and not a very logic
J> behavior.

 No, it's not a bug nor a bug in the documentation.

 What you must understand is that when you write

  Hash.new(Hash.new)

 is like

  default_value = Hash.new
  Hash.new(default_value)

 i.e. default_value is used each times a key is not defined 

 When you write

 var['index2']['index22'] = 'value22'

 because var['index2'] is not defined, ruby will do something like this

  var['index2'] = default_value
  default_value['index22'] = 'value22'

 Same with

  var['index3']['index32'] = 'value32'

 it do

  var['index3'] = default_value
  default_value['index32'] = 'value32'

 When you ask for var['donotexist'] it give you the variable default_value,
 i.e. the hash {"index32" => "value32", "index22" =>"value22"}

 With 1.7 you'll have the possibility to write

 Hash.new { Hash.new }

 and each times a key is not defined, ruby will evaluate the block, the
 result of the block will be stored in the Hash and ruby will do what you
 want.


Guy Decoux