204 lines
8.0 KiB
C++
204 lines
8.0 KiB
C++
/*!
|
|
@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
|