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+/*=============================================================================
+ Copyright (c) 2014 Paul Fultz II
+ static.h
+ Distributed under the Boost Software License, Version 1.0. (See accompanying
+ file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+==============================================================================*/
+
+#ifndef BOOST_HOF_GUARD_FUNCTION_STATIC_H
+#define BOOST_HOF_GUARD_FUNCTION_STATIC_H
+
+/// static
+/// ======
+///
+/// Description
+/// -----------
+///
+/// The `static_` adaptor is a static function adaptor that allows any
+/// default-constructible function object to be static-initialized. Functions
+/// initialized by `static_` cannot be used in `constexpr` functions. If the
+/// function needs to be statically initialized and called in a `constexpr`
+/// context, then a `constexpr` constructor needs to be used rather than
+/// `static_`.
+///
+/// Synopsis
+/// --------
+///
+/// template<class F>
+/// class static_;
+///
+/// Requirements
+/// ------------
+///
+/// F must be:
+///
+/// * [ConstFunctionObject](ConstFunctionObject)
+/// * DefaultConstructible
+///
+/// Example
+/// -------
+///
+/// #include <boost/hof.hpp>
+/// #include <cassert>
+/// using namespace boost::hof;
+///
+/// // In C++ this class can't be static-initialized, because of the non-
+/// // trivial default constructor.
+/// struct times_function
+/// {
+/// double factor;
+/// times_function() : factor(2)
+/// {}
+/// template<class T>
+/// T operator()(T x) const
+/// {
+/// return x*factor;
+/// }
+/// };
+///
+/// static constexpr static_<times_function> times2 = {};
+///
+/// int main() {
+/// assert(6 == times2(3));
+/// }
+///
+
+#include <boost/hof/detail/result_of.hpp>
+#include <boost/hof/reveal.hpp>
+
+namespace boost { namespace hof {
+
+template<class F>
+struct static_
+{
+
+ struct failure
+ : failure_for<F>
+ {};
+
+ const F& base_function() const
+ BOOST_HOF_NOEXCEPT_CONSTRUCTIBLE(F)
+ {
+ static F f;
+ return f;
+ }
+
+ BOOST_HOF_RETURNS_CLASS(static_);
+
+ template<class... Ts>
+ BOOST_HOF_SFINAE_RESULT(F, id_<Ts>...)
+ operator()(Ts && ... xs) const
+ BOOST_HOF_SFINAE_RETURNS(BOOST_HOF_CONST_THIS->base_function()(BOOST_HOF_FORWARD(Ts)(xs)...));
+};
+
+
+}} // namespace boost::hof
+
+#endif