feat():initial version

install/boost_1_75_0/include/boost/hof/static.hpp

@@ -0,0 +1,97 @@
+/*=============================================================================
+    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