Flatten arrays, with compact option

flat.rb

#!/usr/bin/ruby

# A function to flatten arrays, optionally removing any nil elements
#
# ==== Parameters
# * +val+ - a value expected to be an array
# * +compact+ - set to true to remove nil elements
#
def flat(val, compact = false)
  if val.is_a?(Array)
    farr = []
    val.each do |x|
      if x.is_a?(Array)
        farr += flat(x, compact)
      else
        farr << x if (!compact || compact && x)
      end
    end

    # Or,
    #compact ?
    #  val.each { |x|
    #    farr.push *(x.is_a?(Array) ? flat(x, compact) : x) 
    #  }
    #: val.each { |x|
    #  x.is_a?(Array) ? farr += flat(x, compact) : farr << x
    #}

    farr
  else
    val
  end
end

x = [[1,2,[3]],4]
puts "Default"
puts "-------"
puts "Original: "+x.inspect
puts "Expected: "+x.flatten.inspect
puts "  Result: "+flat(x).inspect
puts

x = [nil, [2, nil, [4]], 5, 6]
puts "Compact"
puts "-------"
puts "Original: "+x.inspect
puts "Expected: "+x.flatten.compact.inspect
puts "  Result: "+flat(x, true).inspect
puts

x = 7
puts "Non-array"
puts "---------"
puts "   Result: "+flat(x).inspect
puts