From: Robert Klemme <bob.news@...>
Date: 2005-08-17T19:11:15+09:00
Subject: Extend Class Matrix? (was: Re: Ruby 2 Idea: You've got to have a[a][b][c][d][e][f][g][h][i]...)

Pit Capitain wrote:
> Brian Schr�der schrieb:
>> Though I never had use for this, here is my attempt on an
>> autovivifying array of arrays:
>>
>> class Autoarray < Array
>>   def initialize(size=0, default=nil, update = nil, update_index =
>>     nil) super(size, default)
>>     @update, @update_index = update, update_index
>>   end
>>
>>   def [](k)
>>     if k.abs() < self.length
>>       super(k)
>>     else
>>       Autoarray.new(0, nil, self, k)
>>     end
>>   end
>>
>>   def []=(k, v)
>>     @update[@update_index] = self if @update and @update_index
>>     super
>>   end
>> end
>>
>> a  = Autoarray.new
>> a[1][2][3] = 12
>> a             #=> [nil, [nil, nil, [nil, nil, nil, 12]]]
>> a[2][3][4]    #=> []
>> a             #=> [nil, [nil, nil, [nil, nil, nil, 12]]]
>
> Very nice. There are problems with negative indexes (try a[1][-2][2])
> but I'm sure they can be fixed. I really like the idea.

While reading this thread I thought class Matrix would be a good solution,
but it lacks these properties:

 - factory method that takes dimension sizes instead of actual elements

 - capability to handle more than two dimensions

 - autovivification

How do people think about extending class Matrix of the std lib with these
properties?  We could then have Matrix[3,4,5,10,2] which creates a five
dimensional 3x4x5x10x2 Matrix etc.  Note that this factory method does not
conflict with the old usage Matrix[[1,2],[3,4]] where arrays were used to
provide actual values.

Kind regards

    robert