edwinmeyer

module ArrayTransform

  # Recursively flatten an array by flattening each half of the input array and concatenating the results.  
  # Special cases: 
  # 1) A zero-length array is returned unchanged
  # 2) An array nested inside a single-element array is flattened and returned. 
  # Terminating condition: An array containing a single non-array-element is returned without modification
  def self.flatten(obj)
    raise "flatten: Array required; #{obj.class} provided" unless obj.is_a?(Array)
    olen = obj.length # because we use it multiple times