From: "Ara.T.Howard" <Ara.T.Howard@...>
Date: 2005-08-20T04:41:16+09:00
Subject: Re: Ruby 2 Idea:  You've got to have a[a][b][c][d][e][f][g][h][i]...

On Sat, 20 Aug 2005, mathew wrote:

> Xeno Campanoli wrote:
>> There are just too many problems that can quickly be solved by 
>> multi-dimensional arrays and hashes not to have them and have them easily. 
>> I used the hack from "matz" today to make a 2d hash, and it's ugly and 
>> unworthy of Ruby. You should be able to do this without any extra steps 
>> just like in Perl.  If the project ends up getting bigger THEN you refactor 
>> it, but YOU JUST GOT TO HAVE THAT.
>
> Well, the support for multiple dimensions of index selector is already there. 
> That is, you already have a[a][b][c][d][e][f][g][h][i]..., you just need to 
> create the array to start with. For that part, it's not too hard to write a 
> convenient multi-dimensional array factory method:
>
> require 'pp'
>
> def ArrayFactory(dimensions, initialvalue)
>  size = dimensions.first
>  if dimensions.length == 1
>    return Array.new(size, initialvalue)
>  else
>    rest = dimensions[1,dimensions.length-1]
>    a = Array.new(size)
>    for i in 0..size
>      a[i] = ArrayFactory(rest, initialvalue)
>    end
>    return a
>  end
> end
>
> a = ArrayFactory([3, 5, 7], "Hi!")
> pp a
>
> a[2][3][7] = "Hello!"
> puts a[2][3][7]
> pp a[2][3]
>
> I have to say, though, that I've never had much need for multi-dimensional 
> arrays. Outside the realm of scientific data analysis, most of the time you 
> really want hashes because your "array" is sparse, has unusual bounds, or 
> whatever. At that point you should probably be looking at writing a proper 
> storage class.

or use narray:

     harp:~ > cat a.rb
     require 'narray'

     na = NArray::byte 42, 42, 42

     p na.size
     p na.shape

     na[] = 42
     p na.min
     p na.max
     p na.mean.ceil

     na[] = 0
     na[0 ... (na.size/2)] = 84
     p na.min
     p na.max
     p na.mean.ceil



     harp:~ > time ruby a.rb
     74088
     [42, 42, 42]
     42
     42
     42
     0
     84
     42

     real    0m0.020s
     user    0m0.020s
     sys     0m0.000s


__fast__

-a
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