From: Gavin Sinclair <gsinclair@...>
Date: 2002-08-27T12:02:26+09:00
Subject: Re: Hybrid hash and array?

>> [Phillip:]
>> When programming radio buttons on a website, I find myself using this
>> sort of construct a lot:
>>
>>     @choices = [
>>         ['1', 'Spring'],
>>         ['2', 'Summer'],
>>         ['3', 'Fall']
>>     ]
>>
>>     @table = {}
>>     @choices.each do |key, value|
>>         @table[key] = value
>>     end
>>
>> The data structure I really want is like a hash, except that it
>> maintains its key/value pairs in the order that I defined them.

> [Hal:]
> You could always use Array#assoc...
>
>   @choices.assoc('1')[1]  # 'Spring'
>   @choices.assoc('3')[1]  # 'Fall'
>

[Gavin:]

You can, but it's ugly.  Like Phillip, I have occasionally wanted to
retrieve hash pairs in insertion order.  It seems such a simple request. 
It's not something I expect of the language, but a module would be nice. 
Perl has IxHash for this.  I know absolutely nothing else about it, but
maybe I'll implement it!  (Maybe it already exists on RAA, but I haven't
seen it.)

By the way, to convert array = [[a,1], [c,2], ...] to a hash, you can use:

(hang on, I thought there was a built-in way to do it in one expression -
I must be wrong)

Gavin