/*=============================================================================
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Copyright (c) 2014 Paul Fultz II
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lambda.h
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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==============================================================================*/
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#ifndef BOOST_HOF_GUARD_FUNCTION_LAMBDA_H
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#define BOOST_HOF_GUARD_FUNCTION_LAMBDA_H
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/// BOOST_HOF_STATIC_LAMBDA
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/// =================
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///
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/// Description
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/// -----------
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///
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/// The `BOOST_HOF_STATIC_LAMBDA` macro allows initializing non-capturing lambdas at
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/// compile-time in a `constexpr` expression.
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///
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/// Example
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/// -------
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///
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/// #include <boost/hof.hpp>
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/// #include <cassert>
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///
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/// const constexpr auto add_one = BOOST_HOF_STATIC_LAMBDA(int x)
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/// {
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/// return x + 1;
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/// };
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///
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/// int main() {
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/// assert(3 == add_one(2));
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/// }
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///
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/// BOOST_HOF_STATIC_LAMBDA_FUNCTION
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/// ==========================
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///
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/// Description
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/// -----------
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///
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/// The `BOOST_HOF_STATIC_LAMBDA_FUNCTION` macro allows initializing a global
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/// function object that contains non-capturing lambdas. It also ensures that
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/// the global function object has a unique address across translation units.
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/// This helps prevent possible ODR-violations.
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///
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/// By default, all functions defined with `BOOST_HOF_STATIC_LAMBDA_FUNCTION` use
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/// the `boost::hof::reveal` adaptor to improve error messages.
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///
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/// Example
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/// -------
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///
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/// #include <boost/hof.hpp>
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/// #include <cassert>
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///
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/// BOOST_HOF_STATIC_LAMBDA_FUNCTION(add_one) = [](int x)
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/// {
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/// return x + 1;
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/// };
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/// int main() {
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/// assert(3 == add_one(2));
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/// }
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///
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#include <boost/hof/config.hpp>
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// TODO: Move this to a detail header
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#if !BOOST_HOF_HAS_CONSTEXPR_LAMBDA || !BOOST_HOF_HAS_INLINE_LAMBDAS
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#include <type_traits>
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#include <utility>
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#include <boost/hof/detail/result_of.hpp>
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#include <boost/hof/reveal.hpp>
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#include <boost/hof/detail/constexpr_deduce.hpp>
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#include <boost/hof/function.hpp>
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#ifndef BOOST_HOF_REWRITE_STATIC_LAMBDA
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#ifdef _MSC_VER
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#define BOOST_HOF_REWRITE_STATIC_LAMBDA 1
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#else
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#define BOOST_HOF_REWRITE_STATIC_LAMBDA 0
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#endif
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#endif
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namespace boost { namespace hof {
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namespace detail {
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template<class F>
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struct static_function_wrapper
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{
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// Default constructor necessary for MSVC
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constexpr static_function_wrapper()
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{}
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static_assert(BOOST_HOF_IS_EMPTY(F), "Function or lambda expression must be empty");
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struct failure
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: failure_for<F>
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{};
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template<class... Ts>
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const F& base_function(Ts&&...) const
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{
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return reinterpret_cast<const F&>(*this);
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}
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BOOST_HOF_RETURNS_CLASS(static_function_wrapper);
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template<class... Ts>
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BOOST_HOF_SFINAE_RESULT(const F&, id_<Ts>...)
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operator()(Ts&&... xs) const BOOST_HOF_SFINAE_RETURNS
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(
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BOOST_HOF_RETURNS_REINTERPRET_CAST(const F&)(*BOOST_HOF_CONST_THIS)(BOOST_HOF_FORWARD(Ts)(xs)...)
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);
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};
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struct static_function_wrapper_factor
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{
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constexpr static_function_wrapper_factor()
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{}
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template<class F>
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constexpr static_function_wrapper<F> operator= (const F&) const
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{
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// static_assert(std::is_literal_type<static_function_wrapper<F>>::value, "Function wrapper not a literal type");
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return {};
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}
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};
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#if BOOST_HOF_REWRITE_STATIC_LAMBDA
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template<class T, class=void>
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struct is_rewritable
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: std::false_type
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{};
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template<class T>
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struct is_rewritable<T, typename detail::holder<
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typename T::fit_rewritable_tag
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>::type>
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: std::is_same<typename T::fit_rewritable_tag, T>
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{};
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template<class T, class=void>
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struct is_rewritable1
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: std::false_type
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{};
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template<class T>
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struct is_rewritable1<T, typename detail::holder<
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typename T::fit_rewritable1_tag
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>::type>
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: std::is_same<typename T::fit_rewritable1_tag, T>
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{};
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template<class T, class=void>
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struct rewrite_lambda;
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template<template<class...> class Adaptor, class... Ts>
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struct rewrite_lambda<Adaptor<Ts...>, typename std::enable_if<
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is_rewritable<Adaptor<Ts...>>::value
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>::type>
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{
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typedef Adaptor<typename rewrite_lambda<Ts>::type...> type;
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};
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template<template<class...> class Adaptor, class T, class... Ts>
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struct rewrite_lambda<Adaptor<T, Ts...>, typename std::enable_if<
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is_rewritable1<Adaptor<T, Ts...>>::value
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>::type>
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{
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typedef Adaptor<typename rewrite_lambda<T>::type, Ts...> type;
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};
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template<class T>
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struct rewrite_lambda<T, typename std::enable_if<
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std::is_empty<T>::value &&
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!is_rewritable<T>::value &&
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!is_rewritable1<T>::value
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>::type>
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{
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typedef static_function_wrapper<T> type;
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};
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template<class T>
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struct rewrite_lambda<T, typename std::enable_if<
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!std::is_empty<T>::value &&
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!is_rewritable<T>::value &&
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!is_rewritable1<T>::value
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>::type>
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{
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typedef T type;
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};
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#endif
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template<class T>
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struct reveal_static_lambda_function_wrapper_factor
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{
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constexpr reveal_static_lambda_function_wrapper_factor()
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{}
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#if BOOST_HOF_REWRITE_STATIC_LAMBDA
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template<class F>
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constexpr reveal_adaptor<typename rewrite_lambda<F>::type>
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operator=(const F&) const
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{
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return reveal_adaptor<typename rewrite_lambda<F>::type>();
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}
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#elif BOOST_HOF_HAS_CONST_FOLD
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template<class F>
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constexpr const reveal_adaptor<F>& operator=(const F&) const
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{
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return reinterpret_cast<const reveal_adaptor<F>&>(static_const_var<T>());
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}
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#else
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template<class F>
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constexpr reveal_adaptor<static_function_wrapper<F>> operator=(const F&) const
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{
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return {};
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}
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#endif
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};
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}}} // namespace boost::hof
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#endif
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#if BOOST_HOF_HAS_CONSTEXPR_LAMBDA
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#define BOOST_HOF_STATIC_LAMBDA []
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#else
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#define BOOST_HOF_DETAIL_MAKE_STATIC BOOST_HOF_DETAIL_CONSTEXPR_DEDUCE boost::hof::detail::static_function_wrapper_factor()
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#define BOOST_HOF_STATIC_LAMBDA BOOST_HOF_DETAIL_MAKE_STATIC = []
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#endif
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#if BOOST_HOF_HAS_INLINE_LAMBDAS
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#define BOOST_HOF_STATIC_LAMBDA_FUNCTION BOOST_HOF_STATIC_FUNCTION
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#else
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#define BOOST_HOF_DETAIL_MAKE_REVEAL_STATIC(T) BOOST_HOF_DETAIL_CONSTEXPR_DEDUCE_UNIQUE(T) boost::hof::detail::reveal_static_lambda_function_wrapper_factor<T>()
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#define BOOST_HOF_STATIC_LAMBDA_FUNCTION(name) \
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struct fit_private_static_function_ ## name {}; \
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BOOST_HOF_STATIC_AUTO_REF name = BOOST_HOF_DETAIL_MAKE_REVEAL_STATIC(fit_private_static_function_ ## name)
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#endif
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#endif
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