From: Shannon Fang <xrfang@...>
Date: 2005-10-25T13:46:33+09:00
Subject: Re: RCR: Array#to_h

Ok, we may consider Array#to_h as a true reverse operation of Hash#to_a, 
however, I think the feature I proposed has different usage. May be anyone 
has a better name for easy understanding?

Also, I am not very clear about this code:

>   module Enumerable
>     def to_h
>       hash = {}
>       each {|key, value| hash[key] = value}
>       hash
>     end
>   end
>

Array mixed Eumerable, hence, if use the above code, we have:

arr = [a, b, c, d, e]
arr.to_h     => {1 => a, 2 => b, 3 => c, 4 => d, 5 =>e}

Which seems not very useful, I think the to_h operation of array should use 
array VALUE as the hash KEY.

Shannon


>From: nobuyoshi nakada <nobuyoshi.nakada@ge.com>
>Reply-To: ruby-talk@ruby-lang.org
>To: ruby-talk@ruby-lang.org (ruby-talk ML)
>Subject: Re: RCR: Array#to_h
>Date: Tue, 25 Oct 2005 12:48:40 +0900
>
>Hi,
>
>At Tue, 25 Oct 2005 12:10:18 +0900,
>Shannon Fang wrote in [ruby-talk:162399]:
> > Abstract
> >
> > A simple method that construct a hash from an array. Just like Hash#to_a
> > return an array from hash.
>
>Agreed here, but
>
> > 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}
>
>I expect that method as:
>
>   h = {"foo"=>1,"bar"=>2}
>   a = h.to_a			# => [["foo", 1], ["bar", 2]]
>   a.to_h			# => {"foo"=>1,"bar"=>2} == h
>
>   module Enumerable
>     def to_h
>       hash = {}
>       each {|key, value| hash[key] = value}
>       hash
>     end
>   end
>
>--
>Nobu Nakada
>