class BinData::Array

form returns an empty array.
If the array is empty, the first form returns nil, and the second
Returns the first element, or the first +n+ elements, of the array.

def first(n = nil)
  if n.nil? && empty?
    # explicitly return nil as arrays grow automatically
    nil
  elsif n.nil?
    self[0]
  else
    self[0, n]
  end
end