class REXML::Elements

eles.size # => 5
eles[50] = REXML::Text.new('bar') # => "bar"

if +replacement_element+ is not an \Element:
Does nothing (or raises an exception)

eles[5] # =>
eles.size # => 5
eles[50] = REXML::Element.new('foo') # =>
eles.size # => 4
eles = d.root.elements # => # ... >
d = REXML::Document.new(xml_string)

adds +replacement_element+ to the element and returns
When eles[index] does not exist,

eles[2] # => ...
eles[2] = REXML::Text.new('bar')
eles[2] # => ...
if +replacement_element+ is not an \Element:
Does nothing (or raises an exception)

eles[1] # =>
eles[1] = REXML::Element.new('foo')
eles[1] # => ...
eles = d.root.elements # => # ... >
d = REXML::Document.new(xml_string)

and returns +replacement_element+:
When eles[index] exists, replaces it with +replacement_element+

Replaces or adds an element.

elements[] = index, replacement_element -> replacement_element or nil
:call-seq:

def []=( index, element )
  previous = self[index]
  if previous.nil?
    @element.add element
  else
    previous.replace_with element
  end
  return previous
end