- 
            Peter Dimov suggested the name 'optional', and was the first to point
            out the need for aligned storage.
          
- 
            Douglas Gregor developed 'type_with_alignment', and later Eric Friedman
            coded 'aligned_storage', which are the core of the optional class implementation.
          
- 
            Andrei Alexandrescu and Brian Parker also worked with aligned storage
            techniques and their work influenced the current implementation.
          
- 
            Gennadiy Rozental made extensive and important comments which shaped
            the design.
          
- 
            Vesa Karvonen and Douglas Gregor made quite useful comparisons between
            optional, variant and any; and made other relevant comments.
          
- 
            Douglas Gregor and Peter Dimov commented on comparisons and evaluation
            in boolean contexts.
          
- 
            Eric Friedman helped understand the issues involved with aligned storage,
            move/copy operations and exception safety.
          
- 
            Many others have participated with useful comments: Aleksey Gurotov,
            Kevlin Henney, David Abrahams, and others I can't recall.
          
- 
            William Kempf carefully considered the originally proposed interface
            and suggested the new interface which is currently used. He also started
            and fueled the discussion about the analogy optional<>/smart pointer
            and about relational operators.
          
- 
            Peter Dimov, Joel de Guzman, David Abrahams, Tanton Gibbs and Ian Hanson
            focused on the relational semantics of optional (originally undefined);
            concluding with the fact that the pointer-like interface doesn't make
            it a pointer so it shall have deep relational operators.
          
- 
            Augustus Saunders also explored the different relational semantics between
            optional<> and a pointer and developed the OptionalPointee concept
            as an aid against potential conflicts on generic code.
          
- 
            Joel de Guzman noticed that optional<> can be seen as an API on
            top of variant<T,nil_t>.
          
- 
            Dave Gomboc explained the meaning and usage of the Haskell analog to
            optional<>: the Maybe type constructor (analogy originally pointed
            out by David Sankel).
          
- 
            Other comments were posted by Vincent Finn, Anthony Williams, Ed Brey,
            Rob Stewart, and others.
          
- 
            Joel de Guzman made the case for the support of references and helped
            with the proper semantics.
          
- 
            Mat Marcus shown the virtues of a value-oriented interface, influencing
            the current design, and contributed the idea of "none".
          
- 
            Vladimir Batov's design of Boost.Convert library motivated the development
            of value accessors for optional:
            functionsvalue,value_or,value_or_eval.