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author | DongHun Kwak <dh0128.kwak@samsung.com> | 2019-12-05 15:12:59 +0900 |
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committer | DongHun Kwak <dh0128.kwak@samsung.com> | 2019-12-05 15:12:59 +0900 |
commit | b8cf34c691623e4ec329053cbbf68522a855882d (patch) | |
tree | 34da08632a99677f6b79ecb65e5b655a5b69a67f /boost/hof/static.hpp | |
parent | 3fdc3e5ee96dca5b11d1694975a65200787eab86 (diff) | |
download | boost-b8cf34c691623e4ec329053cbbf68522a855882d.tar.gz boost-b8cf34c691623e4ec329053cbbf68522a855882d.tar.bz2 boost-b8cf34c691623e4ec329053cbbf68522a855882d.zip |
Imported Upstream version 1.67.0upstream/1.67.0
Diffstat (limited to 'boost/hof/static.hpp')
-rw-r--r-- | boost/hof/static.hpp | 97 |
1 files changed, 97 insertions, 0 deletions
diff --git a/boost/hof/static.hpp b/boost/hof/static.hpp new file mode 100644 index 0000000000..2539d93de0 --- /dev/null +++ b/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 |