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