[Boost-users] program_options: documentation dead end

I am trying to understand composing, multitoken and zero_tokens methods of the typed_value class. This link http://www.boost.org/doc/html/boost/program_options/typed_value.html#id69860... is to the composing method from the reference page for the typed_value class: it suggests looking at the is_composing documentation, which is unfortunately empty. Can this be fixed for Boost 1.34.1? Also, can someone explain to me what the multitokens method does. The doc states "Specifies that the value can span multiple tokens." What is the definition of a token here? Finally, what does zero_tokens() do? Thanks in advance Steven