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/*!
@file
Defines `boost::hana::equal`.
@copyright Louis Dionne 2013-2016
Distributed under the Boost Software License, Version 1.0.
(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
*/
#ifndef BOOST_HANA_EQUAL_HPP
#define BOOST_HANA_EQUAL_HPP
#include <boost/hana/fwd/equal.hpp>
#include <boost/hana/accessors.hpp>
#include <boost/hana/all_of.hpp>
#include <boost/hana/and.hpp>
#include <boost/hana/at.hpp>
#include <boost/hana/bool.hpp>
#include <boost/hana/concept/comparable.hpp>
#include <boost/hana/concept/constant.hpp>
#include <boost/hana/concept/product.hpp>
#include <boost/hana/concept/sequence.hpp>
#include <boost/hana/concept/struct.hpp>
#include <boost/hana/config.hpp>
#include <boost/hana/core/common.hpp>
#include <boost/hana/core/to.hpp>
#include <boost/hana/core/dispatch.hpp>
#include <boost/hana/core/tag_of.hpp>
#include <boost/hana/core/when.hpp>
#include <boost/hana/detail/concepts.hpp>
#include <boost/hana/detail/dependent_on.hpp>
#include <boost/hana/detail/has_common_embedding.hpp>
#include <boost/hana/detail/nested_to.hpp> // required by fwd decl
#include <boost/hana/first.hpp>
#include <boost/hana/if.hpp>
#include <boost/hana/length.hpp>
#include <boost/hana/second.hpp>
#include <boost/hana/value.hpp>
#include <cstddef>
BOOST_HANA_NAMESPACE_BEGIN
//! @cond
template <typename X, typename Y>
constexpr auto equal_t::operator()(X&& x, Y&& y) const {
using T = typename hana::tag_of<X>::type;
using U = typename hana::tag_of<Y>::type;
using Equal = equal_impl<T, U>;
return Equal::apply(static_cast<X&&>(x), static_cast<Y&&>(y));
}
//! @endcond
template <typename T, typename U, bool condition>
struct equal_impl<T, U, when<condition>> : default_ {
template <typename X, typename Y>
static constexpr auto apply(X const&, Y const&) {
using T_ = detail::dependent_on_t<sizeof(X) == 1, T>;
static_assert(!hana::is_convertible<T_, U>::value &&
!hana::is_convertible<U, T_>::value,
"No default implementation of hana::equal is provided for related "
"types that can't be safely embedded into a common type, because "
"those are most likely programming errors. If this is really what "
"you want, you can manually convert both objects to a common "
"Comparable type before performing the comparison. If you think "
"you have made your types Comparable but you see this, perhaps you "
"forgot to define some of the necessary methods for an automatic "
"model of Comparable to kick in. A possible culprit is defining "
"'operator==' but not 'operator!='.");
return hana::false_c;
}
};
// Cross-type overload
template <typename T, typename U>
struct equal_impl<T, U, when<
detail::has_nontrivial_common_embedding<Comparable, T, U>::value &&
!detail::EqualityComparable<T, U>::value
>> {
using C = typename hana::common<T, U>::type;
template <typename X, typename Y>
static constexpr auto apply(X&& x, Y&& y) {
return hana::equal(hana::to<C>(static_cast<X&&>(x)),
hana::to<C>(static_cast<Y&&>(y)));
}
};
//////////////////////////////////////////////////////////////////////////
// Model for EqualityComparable data types
//////////////////////////////////////////////////////////////////////////
template <typename T, typename U>
struct equal_impl<T, U, when<detail::EqualityComparable<T, U>::value>> {
template <typename X, typename Y>
static constexpr auto apply(X&& x, Y&& y)
{ return static_cast<X&&>(x) == static_cast<Y&&>(y); }
};
//////////////////////////////////////////////////////////////////////////
// Model for Constants wrapping a Comparable
//////////////////////////////////////////////////////////////////////////
template <typename C>
struct equal_impl<C, C, when<
hana::Constant<C>::value &&
Comparable<typename C::value_type>::value
>> {
template <typename X, typename Y>
static constexpr auto apply(X const&, Y const&) {
constexpr auto eq = hana::equal(hana::value<X>(), hana::value<Y>());
constexpr bool truth_value = hana::if_(eq, true, false);
return hana::bool_<truth_value>{};
}
};
//////////////////////////////////////////////////////////////////////////
// Comparable for Products
//////////////////////////////////////////////////////////////////////////
template <typename T, typename U>
struct equal_impl<T, U, when<hana::Product<T>::value && hana::Product<U>::value>> {
template <typename X, typename Y>
static constexpr auto apply(X const& x, Y const& y) {
return hana::and_(
hana::equal(hana::first(x), hana::first(y)),
hana::equal(hana::second(x), hana::second(y))
);
}
};
//////////////////////////////////////////////////////////////////////////
// Comparable for Sequences
//////////////////////////////////////////////////////////////////////////
namespace detail {
template <typename Xs, typename Ys, std::size_t Length>
struct compare_finite_sequences {
Xs const& xs;
Ys const& ys;
template <std::size_t i>
constexpr auto apply(hana::false_, hana::true_) const {
return compare_finite_sequences::apply<i+1>(
hana::bool_<i+1 == Length>{},
hana::if_(hana::equal(hana::at_c<i>(xs), hana::at_c<i>(ys)),
hana::true_c, hana::false_c)
);
}
template <std::size_t i>
constexpr auto apply(hana::false_, hana::false_) const
{ return hana::false_c; }
template <std::size_t i, typename Result>
constexpr auto apply(hana::true_, Result r) const
{ return r; }
template <std::size_t i>
constexpr bool apply(hana::false_, bool b) const {
return b && compare_finite_sequences::apply<i+1>(
hana::bool_<i+1 == Length>{},
hana::if_(hana::equal(hana::at_c<i>(xs), hana::at_c<i>(ys)),
hana::true_c, hana::false_c)
);
}
};
}
template <typename T, typename U>
struct equal_impl<T, U, when<Sequence<T>::value && hana::Sequence<U>::value>> {
template <typename Xs, typename Ys>
static constexpr auto apply(Xs const& xs, Ys const& ys) {
constexpr std::size_t xs_size = decltype(hana::length(xs))::value;
constexpr std::size_t ys_size = decltype(hana::length(ys))::value;
detail::compare_finite_sequences<Xs, Ys, xs_size> comp{xs, ys};
return comp.template apply<0>(hana::bool_<xs_size == 0>{},
hana::bool_<xs_size == ys_size>{});
}
};
namespace detail {
template <typename X, typename Y>
struct compare_struct_members {
X const& x;
Y const& y;
template <typename Member>
constexpr auto operator()(Member&& member) const {
auto accessor = hana::second(static_cast<Member&&>(member));
return hana::equal(accessor(x), accessor(y));
}
};
}
template <typename S>
struct equal_impl<S, S, when<hana::Struct<S>::value>> {
template <typename X, typename Y>
static constexpr auto apply(X const& x, Y const& y) {
return hana::all_of(hana::accessors<S>(),
detail::compare_struct_members<X, Y>{x, y});
}
};
BOOST_HANA_NAMESPACE_END
#endif // !BOOST_HANA_EQUAL_HPP
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