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/*!
@file
Forward declares `boost::hana::is_a` and `boost::hana::is_an`.
@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_FWD_CORE_IS_A_HPP
#define BOOST_HANA_FWD_CORE_IS_A_HPP
#include <boost/hana/config.hpp>
BOOST_HANA_NAMESPACE_BEGIN
//! @ingroup group-core
//! Returns whether the tag of an object matches a given tag.
//!
//! Given a tag `Tag` and a C++ type `T`, `is_a<Tag, T>` is a compile-time
//! Logical representing whether the tag of `T` is exactly `Tag`. In other
//! words, it is equivalent to
//! @code
//! std::is_same<Tag, tag_of<T>::type>
//! @endcode
//!
//! For convenience, an alternate syntax is provided for using `is_a`.
//! Specifically, `is_a<Tag>` is a function object returning whether the
//! argument it is passed has the given tag. In other words,
//! @code
//! is_a<Tag>(x) == is_a<Tag, decltype(x)>
//! @endcode
//!
//!
//! Example
//! -------
//! @include example/core/is_a.cpp
#ifdef BOOST_HANA_DOXYGEN_INVOKED
template <typename Tag, typename optional_T>
constexpr auto is_a = see-documentation;
#else
template <typename Tag, typename ...T>
struct is_a_t;
template <typename Tag, typename ...T>
constexpr is_a_t<Tag, T...> is_a{};
#endif
//! @ingroup group-core
//! Equivalent to `is_a`; provided for consistency with the rules of the
//! English language.
#ifdef BOOST_HANA_DOXYGEN_INVOKED
template <typename Tag, typename ...T>
constexpr auto is_an = is_a<Tag, T...>;
#else
template <typename Tag, typename ...T>
constexpr is_a_t<Tag, T...> is_an{};
#endif
BOOST_HANA_NAMESPACE_END
#endif // !BOOST_HANA_FWD_CORE_IS_A_HPP
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