From: "NARUSE, Yui" <naruse@...>
Date: 2009-07-20T05:33:27+09:00
Subject: [ruby-core:24446] Re: Hash[[1,2]] => {}  ??

David A. Black wrote:
> On Mon, 20 Jul 2009, NARUSE, Yui wrote:
>> When the number of argument for Hash[] is 1,
>> the argument must be a hash (or hash like object) or an array (or
>> array like).
>>
>> And the array object must be an array of two or one length array.
>> Your code is an array of integer, so the code returns the empty hash.
> 
> I'm not sure I understand the reasoning behind that. It seems awfully
> complicated and hard to follow:
> 
>snip<
>
> I'm not clear on the underlying design principle, I guess. The 1.8
> version seems like it was easier to read; an odd number of arguments
> was wrong, which makes sense (to me) for a hash.

The motivation of thie spec is for an array of key-value arrays.

>> Hash[[[:a,1], [:b,2], [:c]]]
=> {:a=>1, :b=>2, :c=>nil}

So arrays beyond this will be empty.

> Wouldn't it be clearer if Hash[[1,2]] was an error?

How about following,

>> Hash[[[:a,1], [:b,2], [:c], nil]]
=> {:a=>1, :b=>2, :c=>nil}

But raise if the content of argument array is not neither array nor nil,
it maybe adoptable without compatibility problem.

-- 
NARUSE, Yui  <naruse@airemix.jp>