From: Dave Thomas <Dave@...>
Date: 2000-06-08T07:36:13-05:00
Subject: [ruby-talk:03194] Re: 3-d arrays?

Hugh Sasse Staff Elec Eng <hgs@dmu.ac.uk> writes:

> So the sensible thing seems to be to just have a flat array and
> provide methods for the indexing, which is pretty much what I did in C++.
> In C++ you cannot overload [][][], so I suppose that is true for Ruby
> as well, is it?

You can overload [] (and []=, to provide your own array referencing
semantics.


  ## Untested
  class ThreeDArray

    def initialize(maxx, maxy)
        @maxx, @maxy = maxx, maxy
        @content = []        # this is where I'll keep the actual content
    end

    def index(x, y, z)  
      ((x*@maxx) + y)*@maxy + z
    end

    def [](x, y, z)
      @content[index(x, y, z)]
    end

    def []=(x, y, z, newVal)
      @content[index(x, y, z)] = newVal
    end
  end

  # Well, almost untested...

  a = ThreeDArray.new(3, 3)

  for i in 0..2
    for j in 0..2
      for k in 0..2
        a[i, j, k] = i * j * k
      end
    end
  end

  for i in 0..2
    for j in 0..2
      for k in 0..2
        printf "%4d", a[i, j, k]
      end
      puts
    end
    puts
  end

#=>

   0   0   0
   0   0   0
   0   0   0

   0   0   0
   0   1   2
   0   2   4

   0   0   0
   0   2   4
   0   4   8


In fact, it wouldn't be hard to extend this one class to handle
n-dimensional arrays, where 'n' is determined as each object is
created.


Regards


Dave