| /* Copyright 2017 Joaquin M Lopez Munoz. |
| * 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) |
| * |
| * See http://www.boost.org/libs/poly_collection for library home page. |
| */ |
| |
| #ifndef BOOST_TT_DETAIL_IS_LIKELY_STATELESS_LAMBDA_HPP |
| #define BOOST_TT_DETAIL_IS_LIKELY_STATELESS_LAMBDA_HPP |
| |
| #if defined(_MSC_VER) |
| #pragma once |
| #endif |
| |
| #include <boost/type_traits/detail/config.hpp> |
| #include <boost/type_traits/integral_constant.hpp> |
| |
| #if defined(BOOST_TT_HAS_ACCURATE_BINARY_OPERATOR_DETECTION) |
| // |
| // We don't need or use this, just define a dummy class: |
| // |
| namespace boost{ namespace type_traits_detail{ |
| |
| template<typename T> |
| struct is_likely_stateless_lambda : public false_type {}; |
| |
| }} |
| |
| #elif !defined(BOOST_NO_CXX11_LAMBDAS) && !defined(BOOST_NO_CXX11_DECLTYPE) && !defined(BOOST_NO_CXX11_TEMPLATE_ALIASES) && !BOOST_WORKAROUND(BOOST_MSVC, < 1900)\ |
| && !(BOOST_WORKAROUND(BOOST_MSVC, == 1900) && defined(_MANAGED)) |
| |
| #include <boost/type_traits/is_convertible.hpp> |
| #include <boost/type_traits/enable_if.hpp> |
| |
| namespace boost{ |
| |
| namespace type_traits_detail{ |
| |
| /* Stateless lambda expressions have one (and only one) call operator and are |
| * convertible to a function pointer with the same signature. Non-lambda types |
| * could satisfy this too, hence the "likely" qualifier. |
| */ |
| |
| template<typename T> |
| struct has_one_operator_call_helper |
| { |
| template<typename Q> static boost::true_type test(decltype(&Q::operator())*); |
| template<typename> static boost::false_type test(...); |
| |
| using type=decltype(test<T>(nullptr)); |
| }; |
| |
| template<typename T> |
| using has_one_operator_call=typename has_one_operator_call_helper<T>::type; |
| |
| template<typename T> |
| struct equivalent_function_pointer |
| { |
| template<typename Q,typename R,typename... Args> |
| static auto helper(R (Q::*)(Args...)const)->R(*)(Args...); |
| template<typename Q,typename R,typename... Args> |
| static auto helper(R (Q::*)(Args...))->R(*)(Args...); |
| |
| using type=decltype(helper(&T::operator())); |
| }; |
| |
| template<typename T,typename=void> |
| struct is_likely_stateless_lambda : false_type{}; |
| |
| template<typename T> |
| struct is_likely_stateless_lambda< |
| T, |
| typename boost::enable_if_<has_one_operator_call<T>::value>::type> : |
| boost::is_convertible<T, typename equivalent_function_pointer<T>::type |
| >{}; |
| |
| } /* namespace type_traits_detail */ |
| |
| } /* namespace boost */ |
| |
| #else |
| // |
| // Can't implement this: |
| // |
| namespace boost { |
| namespace type_traits_detail { |
| |
| template<typename T> |
| struct is_likely_stateless_lambda : public boost::integral_constant<bool, false> {}; |
| }} |
| |
| #endif |
| #endif |
| |