Helping someone who asked in #ruby about recursively replacing Array elements.

gistfile1.builder

b = lambda { |e| e.kind_of?(Array) ? e.map(&b) : (e.nil? ? "" : e) }
# => #<Proc:0x0000000104d908@(irb):1 (lambda)> 

arr = [5, 6, 7, nil, [nil], [6, 8, nil], [[194, 48, nil], [nil]]]
# => [5, 6, 7, nil, [nil], [6, 8, nil], [[194, 48, nil], [nil]]] 

arr.map(&b)
# => [5, 6, 7, "", [""], [6, 8, ""], [[194, 48, ""], [""]]]