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
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:
functions value, value_or, value_or_eval.