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/* Copyright (C) 2016 Murray Cumming
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 3.0 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifndef SIGC_TUPLE_UTILS_TUPLE_FOR_EACH_H
#define SIGC_TUPLE_UTILS_TUPLE_FOR_EACH_H
#include <tuple>
namespace sigc
{
namespace internal
{
namespace detail
{
template <template <typename> class T_visitor, std::size_t size_from_index, typename... T_extras>
struct tuple_for_each_impl
{
template <typename T>
constexpr static void tuple_for_each(T&& t, T_extras&&... extras)
{
// We use std::decay_t<> because tuple_size is not defined for references.
constexpr auto size = std::tuple_size<std::decay_t<T>>::value;
static_assert(size > 1, "size must be more than 0.");
constexpr auto index = size - size_from_index;
static_assert(index >= 0, "unexpected index.");
using element_type = typename std::tuple_element<index, std::decay_t<T>>::type;
T_visitor<element_type>::visit(std::get<index>(t), std::forward<T_extras>(extras)...);
tuple_for_each_impl<T_visitor, size_from_index - 1, T_extras...>::tuple_for_each(
std::forward<T>(t), std::forward<T_extras>(extras)...);
}
};
template <template <typename> class T_visitor, typename... T_extras>
struct tuple_for_each_impl<T_visitor, 1, T_extras...>
{
template <typename T>
constexpr static void tuple_for_each(T&& t, T_extras&&... extras)
{
// We use std::decay_t<> because tuple_size is not defined for references.
constexpr auto size = std::tuple_size<std::decay_t<T>>::value;
static_assert(size > 0, "size must be more than 0.");
constexpr auto index = size - 1;
static_assert(index >= 0, "unexpected index.");
using element_type = typename std::tuple_element<index, std::decay_t<T>>::type;
T_visitor<element_type>::visit(
std::get<index>(std::forward<T>(t)), std::forward<T_extras>(extras)...);
}
};
template <template <typename> class T_visitor, typename... T_extras>
struct tuple_for_each_impl<T_visitor, 0, T_extras...>
{
template <typename T>
constexpr static void tuple_for_each(T&& /* t */, T_extras&&... /* extras */)
{
// Do nothing because the tuple has no elements.
}
};
} // detail namespace
/**
* Call the @e T_Visitor functors visit() method for each element,
* from the first to the last.
*
* @tparam T_visitor should be a template that has a static visit() method.
* @tparam T the tuple type.
* @tparam T_extras the types of any extra arguments to pass to @e T_Visitor's
* visit() method.
* @param t The tuple whose elements should be visited.
* @param extras Any extra arguments to pass to @e T_Visitor's visit() method.
*/
template <template <typename> class T_visitor, typename T, typename... T_extras>
constexpr void
tuple_for_each(T&& t, T_extras&&... extras)
{
// We use std::decay_t<> because tuple_size is not defined for references.
constexpr auto size = std::tuple_size<std::decay_t<T>>::value;
if constexpr (size != 0)
{
detail::tuple_for_each_impl<T_visitor, size, T_extras...>::tuple_for_each(
std::forward<T>(t), std::forward<T_extras>(extras)...);
} else {
// Prevent 'unreferenced formal parameter' warning from MSVC by 'using' t
static_cast<void>(t);
}
}
} // namespace internal
} // namespace sigc
#endif // SIGC_TUPLE_UTILS_TUPLE_FOR_EACH_H
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