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Make pointer_traits SFINAE friendly

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Glen Fernandes
2021-12-12 19:03:57 -05:00
parent 6da7958281
commit 0e62373aa2
7 changed files with 397 additions and 150 deletions
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101
test/pointer_traits_sfinae_test.cpp Normal file
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/*
Copyright 2021 Glen Joseph Fernandes
(glenjofe@gmail.com)
Distributed under the Boost Software License, Version 1.0.
(http://www.boost.org/LICENSE_1_0.txt)
*/
#include <boost/core/pointer_traits.hpp>
#include <boost/core/lightweight_test.hpp>
template<class>
struct valid {
typedef void type;
};
template<class, class = void>
struct has_pointer {
static const bool value = false;
};
template<class T>
struct has_pointer<T, typename valid<typename T::pointer>::type> {
static const bool value = true;
};
template<class, class = void>
struct has_element_type {
static const bool value = false;
};
template<class T>
struct has_element_type<T, typename valid<typename T::element_type>::type> {
static const bool value = true;
};
template<class, class = void>
struct has_difference_type {
static const bool value = false;
};
template<class T>
struct has_difference_type<T,
typename valid<typename T::difference_type>::type> {
static const bool value = true;
};
template<class, class, class = void>
struct has_rebind_to_type {
static const bool value = false;
};
template<class T, class U>
struct has_rebind_to_type<T, U,
typename valid<typename T::template rebind_to<U>::type>::type> {
static const bool value = true;
};
struct P1 { };
struct P2 {
typedef int element_type;
};
struct P3 {
typedef int element_type;
template<class>
struct rebind { };
};
template<class T>
struct S {
typedef T element_type;
};
typedef S<int> P4;
int main()
{
BOOST_TEST(!has_pointer<boost::pointer_traits<P1> >::value);
BOOST_TEST(!has_element_type<boost::pointer_traits<P1> >::value);
BOOST_TEST(!has_difference_type<boost::pointer_traits<P1> >::value);
BOOST_TEST((!has_rebind_to_type<boost::pointer_traits<P1>, char>::value));
BOOST_TEST(has_pointer<boost::pointer_traits<P2> >::value);
BOOST_TEST(has_element_type<boost::pointer_traits<P2> >::value);
BOOST_TEST(has_difference_type<boost::pointer_traits<P2> >::value);
BOOST_TEST((!has_rebind_to_type<boost::pointer_traits<P2>, char>::value));
BOOST_TEST(has_pointer<boost::pointer_traits<P3> >::value);
BOOST_TEST(has_element_type<boost::pointer_traits<P3> >::value);
BOOST_TEST(has_difference_type<boost::pointer_traits<P3> >::value);
BOOST_TEST((has_rebind_to_type<boost::pointer_traits<P3>, char>::value));
BOOST_TEST(has_pointer<boost::pointer_traits<P4> >::value);
BOOST_TEST(has_element_type<boost::pointer_traits<P4> >::value);
BOOST_TEST(has_difference_type<boost::pointer_traits<P4> >::value);
BOOST_TEST((has_rebind_to_type<boost::pointer_traits<P4>, char>::value));
BOOST_TEST(has_pointer<boost::pointer_traits<int*> >::value);
BOOST_TEST(has_element_type<boost::pointer_traits<int*> >::value);
BOOST_TEST(has_difference_type<boost::pointer_traits<int*> >::value);
BOOST_TEST((has_rebind_to_type<boost::pointer_traits<int*>, char>::value));
return boost::report_errors();
}