Ruby multidimensional array

Question

Maybe it\'s just my lack of abilities to find stuff here that is the problem, but I can\'t find anything about how to create multidimensional arrays in Ruby.

Could s

Answer 1

Perhaps you can simulate your multidimensional Array with a Hash. The Hash-key can by any Ruby object, so you could also take an array.

Example:

marray = {}
p marray[[1,2]]   #-> nil
marray[[1,2]] = :a
p marray[[1,2]]   #-> :a

Based on this idea you could define a new class.

Just a quick scenario:

=begin rdoc
Define a multidimensional array.

The keys must be Fixnum.

The following features from Array are not supported:
* negative keys (Like Array[-1])
* No methods <<, each, ...
=end
class MArray
  INFINITY = Float::INFINITY
=begin rdoc
=end
  def initialize(dimensions=2, *limits)
    @dimensions = dimensions
    raise ArgumentError if limits.size > dimensions
    @limits = []
    0.upto(@dimensions-1){|i|
      @limits << (limits[i] || INFINITY)
    }
    @content = {}
  end
  attr_reader :dimensions
  attr_reader :limits
=begin rdoc
=end
  def checkkeys(keys)
    raise ArgumentError, "Additional key values for %i-dimensional Array" % @dimensions if keys.size > @dimensions
    raise ArgumentError, "Missing key values for %i-dimensional Array" % @dimensions if keys.size != @dimensions
    raise ArgumentError, "No keys given" if keys.size == 0
    keys.each_with_index{|key,i|
      raise ArgumentError, "Exceeded limit for %i dimension" % (i+1) if key > @limits[i]
      raise ArgumentError, "Only positive numbers allowed" if key < 1

    }
  end
  def[]=(*keys)
    data = keys.pop
    checkkeys(keys)
    @content[keys] = data
  end
  def[](*keys)
    checkkeys(keys)
    @content[keys]
  end
end

This can be used as:

arr = MArray.new()
arr[1,1] = 3
arr[2,2] = 3

If you need a predefined matrix 2x2 you can use it as:

arr = MArray.new(2,2,2)
arr[1,1] = 3
arr[2,2] = 3
#~ arr[3,2] = 3  #Exceeded limit for 1 dimension (ArgumentError)

I could imagine how to handle commands like << or each in a two-dimensional array, but not in multidimensional ones.