# N-dimensional array in Ruby **URL:** \ **Category:** ruby-talk\ **Created:** [1 November 2008 00:09 UTC](https://rubytalk.org/t/n-dimensional-array-in-ruby/49937 "2008-11-01T00:09:03Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![Christian4](https://avatars.discourse-cdn.com/v4/letter/c/e9c0ed/32.png) [@Christian4](https://rubytalk.org/u/Christian4)\ **Post date:** [1 November 2008 00:09 UTC](https://rubytalk.org/t/n-dimensional-array-in-ruby/49937/1 "2008-11-01T00:09:03Z")
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? ---
**Author:** ![Michael\_Guterl1](https://avatars.discourse-cdn.com/v4/letter/m/e47c2d/32.png) [@Michael\_Guterl1](https://rubytalk.org/u/Michael_Guterl1)\ **Post date:** [1 November 2008 00:29 UTC](https://rubytalk.org/t/n-dimensional-array-in-ruby/49937/2 "2008-11-01T00:29:59Z")
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 Guterl > **···** > > On Fri, Oct 31, 2008 at 8:09 PM, Christian \ wrote: > > > 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? ---
**Author:** ![Mike\_Gold](https://avatars.discourse-cdn.com/v4/letter/m/e480ec/32.png) [@Mike\_Gold](https://rubytalk.org/u/Mike_Gold)\ **Post date:** [1 November 2008 00:45 UTC](https://rubytalk.org/t/n-dimensional-array-in-ruby/49937/3 "2008-11-01T00:45:27Z")
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 > **···** > > -- > Posted via [http://www.ruby-forum.com/\](http://www.ruby-forum.com/%5C). ---
**Author:** ![Mike\_Gold](https://avatars.discourse-cdn.com/v4/letter/m/e480ec/32.png) [@Mike\_Gold](https://rubytalk.org/u/Mike_Gold)\ **Post date:** [1 November 2008 09:04 UTC](https://rubytalk.org/t/n-dimensional-array-in-ruby/49937/4 "2008-11-01T09:04:06Z")
Mike Gold 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|     Array.new(dim) { Marshal.load(Marshal.dump(result)) }   } end > **···** > > -- > Posted via [http://www.ruby-forum.com/\](http://www.ruby-forum.com/%5C). ---
**Author:** ![Brian\_Adkins](https://avatars.discourse-cdn.com/v4/letter/b/3ab097/32.png) [@Brian\_Adkins](https://rubytalk.org/u/Brian_Adkins)\ **Post date:** [1 November 2008 16:43 UTC](https://rubytalk.org/t/n-dimensional-array-in-ruby/49937/5 "2008-11-01T16:43:57Z")
Michael Guterl \ writes: > > 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? > > 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 Thomas, maybe you could add a bit about Infinity in the next relase of Programming Ruby or Programming Ruby 1.9 > **···** > > > On Fri, Oct 31, 2008 at 8:09 PM, Christian \ wrote: > > > a = [,,] > > a[0][0][0] = 0 > > a[0][0][1] = Infinity > > > > The arrays will grow to whatever size you need them to. > > > > HTH, > > Michael Guterl ---
**Author:** ![Brian\_Adkins](https://avatars.discourse-cdn.com/v4/letter/b/3ab097/32.png) [@Brian\_Adkins](https://rubytalk.org/u/Brian_Adkins)\ **Post date:** [1 November 2008 16:43 UTC](https://rubytalk.org/t/n-dimensional-array-in-ruby/49937/6 "2008-11-01T16:43:55Z")
Mike Gold \ writes: > Mike Gold 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| >     Array.new(dim) { Marshal.load(Marshal.dump(result)) } >   } > end Yearning for macros... ---
**Author:** ![Michael\_Guterl1](https://avatars.discourse-cdn.com/v4/letter/m/e47c2d/32.png) [@Michael\_Guterl1](https://rubytalk.org/u/Michael_Guterl1)\ **Post date:** [1 November 2008 17:03 UTC](https://rubytalk.org/t/n-dimensional-array-in-ruby/49937/7 "2008-11-01T17:03:19Z")
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 Guterl > **···** > > On Sat, Nov 1, 2008 at 12:43 PM, Brian Adkins \ wrote: > > > Michael Guterl \ writes: > > > > > On Fri, Oct 31, 2008 at 8:09 PM, Christian \ wrote: > > > > > > > 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? > > > > > > 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 Thomas, maybe > > you could add a bit about Infinity in the next relase of Programming > > Ruby or Programming Ruby 1.9