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Add support for member function to member_ptr #449

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Add support for member function to member_ptr #449

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24c5a6e
Add support for member function to member_ptr
sdebionne Jun 5, 2019
daa802d
Refactor to add symmetry with member object
sdebionne Jun 11, 2019
238714a
Add member function test for struct concept
sdebionne Jun 11, 2019
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9 changes: 7 additions & 2 deletions include/boost/hana/detail/struct_macros.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -29,15 +29,20 @@ Distributed under the Boost Software License, Version 1.0.
#include <boost/hana/tuple.hpp>

#include <cstddef>
#include <type_traits>
#include <utility>


BOOST_HANA_NAMESPACE_BEGIN namespace struct_detail {
template <typename Memptr, Memptr ptr>
struct member_ptr {
template <typename T>
constexpr decltype(auto) operator()(T&& t) const
template <typename T, typename Memptr2 = Memptr, std::enable_if_t<std::is_member_object_pointer_v<Memptr2>, int> = 0>
constexpr decltype(auto) operator()(T && t) const
{ return static_cast<T&&>(t).*ptr; }

template <typename T, typename Memptr2 = Memptr, std::enable_if_t<std::is_member_function_pointer_v<Memptr2>, int> = 0>
constexpr decltype(auto) operator()(T && t) const
{ return [&](auto ... args) { return static_cast<T&&>(t).*ptr(args...); }; }
};

constexpr std::size_t strlen(char const* s) {
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12 changes: 10 additions & 2 deletions include/boost/hana/detail/struct_macros.hpp.erb
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Expand Up @@ -54,9 +54,17 @@ Distributed under the Boost Software License, Version 1.0.
BOOST_HANA_NAMESPACE_BEGIN namespace struct_detail {
template <typename Memptr, Memptr ptr>
struct member_ptr {
template <typename T>
constexpr decltype(auto) operator()(T&& t) const
template <typename Memptr2, typename T, std::enable_if_t<std::is_member_object_pointer_v<Memptr2>, int> = 0>
constexpr decltype(auto) dispatch(T && t) const
{ return static_cast<T&&>(t).*ptr; }

template <typename Memptr2, typename T, std::enable_if_t<std::is_member_function_pointer_v<Memptr2>, int> = 0>
constexpr decltype(auto) dispatch(T && t) const
{ return [&](auto ... args) { return static_cast<T&&>(t).*ptr(args...); }; }

template <typename T>
constexpr decltype(auto) operator()(T && t) const
{ return dispatch<Memptr>(t); }
};

constexpr std::size_t strlen(char const* s) {
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10 changes: 10 additions & 0 deletions test/concept/struct/macro.adapt_struct.cpp
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Expand Up @@ -30,19 +30,24 @@ namespace ns {
struct MemberArray {
int array[10];
};
struct MemberFunction {
int memfun(int x) { return x + 1; }
};
}

BOOST_HANA_ADAPT_STRUCT(ns::Data0);
BOOST_HANA_ADAPT_STRUCT(ns::Data1, member1);
BOOST_HANA_ADAPT_STRUCT(ns::Data2, member1, member2);
BOOST_HANA_ADAPT_STRUCT(ns::Data3, member1, member2, member3);
BOOST_HANA_ADAPT_STRUCT(ns::MemberArray, array);
BOOST_HANA_ADAPT_STRUCT(ns::MemberFunction, memfun);

static_assert(hana::Struct<ns::Data0>::value, "");
static_assert(hana::Struct<ns::Data1>::value, "");
static_assert(hana::Struct<ns::Data2>::value, "");
static_assert(hana::Struct<ns::Data3>::value, "");
static_assert(hana::Struct<ns::MemberArray>::value, "");
static_assert(hana::Struct<ns::MemberFunction>::value, "");

int main() {
BOOST_HANA_CONSTANT_CHECK(hana::contains(ns::Data1{}, BOOST_HANA_STRING("member1")));
Expand All @@ -55,4 +60,9 @@ int main() {
BOOST_HANA_CONSTANT_CHECK(hana::contains(ns::Data3{}, BOOST_HANA_STRING("member3")));

BOOST_HANA_CONSTANT_CHECK(hana::contains(ns::MemberArray{}, BOOST_HANA_STRING("array")));

BOOST_HANA_CONSTANT_CHECK(hana::contains(ns::MemberFunction{}, BOOST_HANA_STRING("memfun")));

constexpr auto accessors = hana::accessors<ns::MemberFunction>();
BOOST_HANA_RUNTIME_CHECK(hana::second(accessors[hana::size_c<0>])(ns::MemberFunction{})(1) == 2);
}