598bfd3f
 Hu Chunming
提交_GLIBCXX_USE_CX...
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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
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