From: Yukihiro Matsumoto <matz@...>
Date: 2005-10-25T15:17:00+09:00
Subject: Re: RCR: Array#to_h

Hi,

In message "Re: RCR: Array#to_h"
    on Tue, 25 Oct 2005 12:10:18 +0900, "Shannon Fang" <xrfang@hotmail.com> writes:

|Abstract
|
|A simple method that construct a hash from an array. Just like Hash#to_a 
|return an array from hash.
|
|Problem
|
|Consider this cenario: I programmed a multi-threaded web page downloader. 
|One of its input is an array of urls to download. In the program, I wanted 
|to use a hash like {'http://ruby-lang.org/index.html' => '200'}, i.e., use a 
|hash to record the return code of the http request. This way I can avoid 
|re-download a page, or miss a page.
|
|For the user of this download program, it is much easier to use an Array 
|instead of a Hash:
|
|d = WebPageDownloader.new
|d.links = IO.readlines('list.txt')
|
|Hence, in the program we want to do:
|
|@links = @links.to_h
|
|Proposal
|
|Add a method to_h (not to_hash) in the Array class, so that user can:
|
|a = [1, 2, 3, 4, 5]
|p a.to_h { |i, v| v * 2}  --> {5=>10, 1=>2, 2=>4, 3=>6, 4=>8}
|p a.to_h(3)                 --> {5=>3, 1=>3, 2=>3, 3=>3, 4=>3}

Rejected.  Proposal Array#to_h(value=nil) does not actually solve the
problem above.  If you want to have _this_ to_h, you need to have
a proper usecase.

							matz.