# N-dimensional array in Ruby

Hi,

i have a little Java problem, I want to solve using Ruby. Therefor I
need an n-dimensional array. In Java it looks like this:

double dArray[][][] = new double[x.length()+1][y.length()+1][x.length()
+y.length()+3];
dArray[0][0][0] = 0;
dArray[0][0][1] = POSITIVE_INFINITY;

Further values will be computed through loops and written into the
array.

How do I initialize such an array in Ruby?

On Fri, Oct 31, 2008 at 8:09 PM, Christian [email protected]
wrote:

Further values will be computed through loops and written into the
array.

How do I initialize such an array in Ruby?

Infinity = 1.0/0

a = [[],[],[]]
a[0][0][0] = 0
a[0][0][1] = Infinity

The arrays will grow to whatever size you need them to.

HTH,
Michael G.

Christian wrote:

i have a little Java problem, I want to solve using Ruby. Therefor I
need an n-dimensional array.

def Array.multi(*dimensions)
dimensions.reverse.inject(nil) { |result, dim|
Array.new(dim) { result ? result.dup : nil }
}
end

a = Array.multi(3, 4, 5)

p a[0] #=> [[nil, nil, …], … ]
p a[0][0] #=> [nil, nil, nil, nil, nil]

a[0][0][0] = :fred
a[2][3][4] = :barney

p a[0][0][0] #=> :fred
p a[2][3][4] #=> :barney

a[3][0][0]

# => exception: undefined method `[]’ for nil; index past dim size

Mike G. [email protected] writes:

dimensions.reverse.inject(nil) { |result, dim|
}
end

Yearning for macros…

Mike G. wrote:

def Array.multi(*dimensions)
dimensions.reverse.inject(nil) { |result, dim|
Array.new(dim) { result ? result.dup : nil }
}
end

My mistake. Array#dup is not a recursive deep copy.

def Array.multi(*dimensions)
dimensions.reverse.inject(nil) { |result, dim|
}
end

Michael G. [email protected] writes:

Further values will be computed through loops and written into the
array.

How do I initialize such an array in Ruby?

Infinity = 1.0/0

~\$ irb
irb(main):001:0> X = 7
=> 7
irb(main):002:0> Infinity = 1.0/0
=> Infinity
irb(main):003:0> 0 / Infinity
=> 0.0
irb(main):004:0> Infinity * Infinity
=> Infinity
irb(main):005:0> Beyond = Infinity
=> Infinity
irb(main):006:0> 2 * Infinity and Beyond
=> Infinity
irb(main):007:0> Infinity.infinite?
=> 1

Cool - I just learned about Infinity in Ruby. Hey Dave T., maybe
you could add a bit about Infinity in the next relase of Programming
Ruby or Programming Ruby 1.9

On Sat, Nov 1, 2008 at 12:43 PM, Brian A. [email protected]
wrote:

dArray[0][0][0] = 0;
irb(main):001:0> X = 7
=> Infinity
irb(main):007:0> Infinity.infinite?
=> 1

Cool - I just learned about Infinity in Ruby. Hey Dave T., maybe
you could add a bit about Infinity in the next relase of Programming
Ruby or Programming Ruby 1.9

Yeah, I don’t think I’ve seen it discussed in any books before, but I
could be wrong.

I stumbled upon it accidentally one day when playing with ruby and
it’s rules for division.

Michael G.