From: Robert Klemme <shortcutter@...>
Date: 2006-10-30T06:45:12+09:00
Subject: Re: Define a hash using %q?

David Vallner wrote:
> Robert Klemme wrote:
>> Logan Capaldo wrote:
>>> Alternative decandence:
>>>
>>> class Array
>>>   def to_hsh
>>>     require 'enumerator'
>>>     to_enum(:each_slice, 2).to_a.inject({}) { |h, (k, v)|
>>> h.update(k=>v) }
>>>   end
>>> end
>> This seems a bit inefficient.  If you write a method then I'd prefer
>>
>> require 'enumerator'
>> module Enumerable
>>   def to_hash
>>     h = {}
>>     to_enum(:each_slice, 2).each {|k,v| h[k]=v}
>>     h
>>   end
>> end
>>
>> irb(main):021:0> %w( a b c d ).to_hash
>> => {"a"=>"b", "c"=>"d"}
>> irb(main):022:0> (1..10).to_hash
>> => {5=>6, 1=>2, 7=>8, 3=>4, 9=>10}
>>
> 
> Well, if Ruby had clean blocks, the method using #inject might be more
> efficient - I don't know how expensive the implicit hash construction
> for method parameters is. Smalltalk muscle memory working there?

I am not sure what you are at here.  Object creation always costs - even 
   small hashes.  Reason is memory allocation and GC management overhead.

Regards

	robert