Better documentation.

README.md

@@ -43,6 +43,7 @@ The primary site for documentation is the automatically generated [API documenta
 * Thread safe, immutable `Either` and `Option` classes based on [Functional Java](http://functionaljava.org/) and [Haskell](https://hackage.haskell.org/package/base-4.2.0.1/docs/Data-Either.html).
 * [Memoization](http://en.wikipedia.org/wiki/Memoization) of class methods based on Clojure [memoize](http://clojuredocs.org/clojure_core/clojure.core/memoize).
 * Lazy execution with a `Delay` class based on Clojure [delay](http://clojuredocs.org/clojure_core/clojure.core/delay).
+* `ValueStruct`, a simple, thread safe, immutable variation of Ruby's [OpenStruct](http://ruby-doc.org/stdlib-2.0/libdoc/ostruct/rdoc/OpenStruct.html) class.
 * Thread safe data structures, such as `FinalStruct` and `FinalVar`, which can be written to at most once
   before becoming immutable. Based on [Java's `final` keyword](http://en.wikipedia.org/wiki/Final_(Java)).
 

lib/functional/abstract_struct.rb

@@ -12,6 +12,7 @@
 module Functional
 
   # An abstract base class for immutable struct classes.
+  # @!visibility private
   module AbstractStruct
 
     # @return [Array] the values of all record fields in order, frozen

lib/functional/option.rb

@@ -15,7 +15,6 @@ module Functional
   # This type is a replacement for the use of nil with better type checks. 
   # It is an immutable data structure that extends `AbstractStruct`.
   #
-  # @see Functional::AbstractStruct
   # @see http://functionaljava.googlecode.com/svn/artifacts/3.0/javadoc/index.html Functional Java
   #
   # @!macro thread_safe_immutable_object

lib/functional/record.rb

@@ -17,7 +17,6 @@ module Functional
   #
   # {include:file:doc/record.md}
   #
-  # @see Functional::AbstractStruct
   # @see Functional::Union
   # @see Functional::Protocol
   # @see Functional::TypeCheck

lib/functional/union.rb

@@ -48,7 +48,6 @@ module Functional
   #   Functional::Union::Suit.hearts('Queen')
   #    #=> #<union Functional::Union::Suit :clubs=>nil, :diamonds=>nil, :hearts=>"Queen", :spades=>nil>
   #
-  # @see Functional::AbstractStruct
   # @see Functional::Union
   # @see http://www.ruby-doc.org/core-2.1.2/Struct.html Ruby `Struct` class
   # @see http://en.wikipedia.org/wiki/Union_type "Union type" on Wikipedia