Copyright (C) 2011-2012 Andrzej Krzemienski

Distributed under the Boost Software License, Version 1.0
(see accompanying file LICENSE_1_0.txt or a copy at
http://www.boost.org/LICENSE_1_0.txt)

The idea and interface is based on Boost.Optional library
authored by Fernando Luis Cacciola Carballal

Home at https://github.com/akrzemi1/Optional