Question

Is there an elegant way to find and replace any integers superior to 3 (as example) in a multidimensional array? The array may have the dimension 1, 2, 3, or more. Just an example of a such array:

[ [ [ 3, 3, 5 ], 
    [ 4, 3, 3 ] ], 
  [ [ 3, 2, 3 ], 
    [ 0, 3, 8 ] ] ]

I would like to do so without flatten the array.

Answer 1

Following sepp2k idea, here is a possible implementation:

class Object
  def deep_map(&block)
    if self.respond_to? :each
      result = []
      self.each do |e|
        result << e.deep_map(&block)
      end
      return result
    else
      return block.call(self)
    end
  end  
end

Then apply deep_map as you wish on the array:

> [[[3, 3, 5], [4, 3, 3]], [[3, 2, 3], [0, 3, 8]]].deep_map { |e| e > 3 ? 0 : e }
=> [[[3, 3, 0], [0, 3, 3]], [[3, 2, 3], [0, 3, 0]]] 

Or, more briefly:

class Object
  def deep_map(&block)
    respond_to?(:map) ? map{|e| e.deep_map(&block)} : block.call(self)
  end
end

Or, polymorphically:

class Object
  def deep_map(&block); block.call(self) end
end

class Array
  def deep_map(&block); map{|e| e.deep_map(&block)} end
end