You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
116 lines
3.3 KiB
116 lines
3.3 KiB
5 years ago
|
/*=============================================================================
|
||
|
|
Copyright (c) 2016 Paul Fultz II
|
||
|
|
is_unpackable.hpp
|
||
|
|
Distributed under the Boost Software License, Version 1.0. (See accompanying
|
||
|
|
file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
|
||
|
|
==============================================================================*/
|
||
|
|
|
||
|
|
#ifndef BOOST_HOF_GUARD_IS_UNPACKABLE_HPP
|
||
|
|
#define BOOST_HOF_GUARD_IS_UNPACKABLE_HPP
|
||
|
|
|
||
|
|
/// is_unpackable
|
||
|
|
/// =============
|
||
|
|
///
|
||
|
|
/// This is a trait that can be used to detect whether the type can be called
|
||
|
|
/// with `unpack`.
|
||
|
|
///
|
||
|
|
/// Synopsis
|
||
|
|
/// --------
|
||
|
|
///
|
||
|
|
/// template<class T>
|
||
|
|
/// struct is_unpackable;
|
||
|
|
///
|
||
|
|
/// Example
|
||
|
|
/// -------
|
||
|
|
///
|
||
|
|
/// #include <boost/hof.hpp>
|
||
|
|
/// #include <cassert>
|
||
|
|
///
|
||
|
|
/// int main() {
|
||
|
|
/// static_assert(boost::hof::is_unpackable<std::tuple<int>>::value, "Failed");
|
||
|
|
/// }
|
||
|
|
///
|
||
|
|
|
||
|
|
#include <boost/hof/unpack_sequence.hpp>
|
||
|
|
#include <boost/hof/is_invocable.hpp>
|
||
|
|
#include <boost/hof/always.hpp>
|
||
|
|
#include <boost/hof/detail/static_const_var.hpp>
|
||
|
|
#include <boost/hof/detail/unpack_tuple.hpp>
|
||
|
|
|
||
|
|
namespace boost { namespace hof {
|
||
|
|
|
||
|
|
namespace detail {
|
||
|
|
|
||
|
|
struct unpack_impl_f
|
||
|
|
{
|
||
|
|
template<class F, class Sequence>
|
||
|
|
constexpr auto operator()(F&& f, Sequence&& s) const BOOST_HOF_RETURNS
|
||
|
|
(
|
||
|
|
boost::hof::unpack_sequence<typename std::remove_cv<typename std::remove_reference<Sequence>::type>::type>::
|
||
|
|
apply(BOOST_HOF_FORWARD(F)(f), BOOST_HOF_FORWARD(Sequence)(s))
|
||
|
|
);
|
||
|
|
};
|
||
|
|
|
||
|
|
BOOST_HOF_DECLARE_STATIC_VAR(unpack_impl, unpack_impl_f);
|
||
|
|
|
||
|
|
#if BOOST_HOF_CHECK_UNPACK_SEQUENCE
|
||
|
|
struct private_unpack_type {};
|
||
|
|
template<class Sequence>
|
||
|
|
struct unpack_impl_result
|
||
|
|
{
|
||
|
|
static_assert(boost::hof::is_invocable<unpack_impl_f, decltype(boost::hof::always(private_unpack_type())), Sequence>::value,
|
||
|
|
"Unpack is invalid for this sequence. The function used to unpack this sequence is not callable."
|
||
|
|
);
|
||
|
|
typedef decltype(boost::hof::detail::unpack_impl(boost::hof::always(private_unpack_type()), std::declval<Sequence>())) type;
|
||
|
|
};
|
||
|
|
|
||
|
|
template<class Sequence>
|
||
|
|
struct is_proper_sequence
|
||
|
|
: std::is_same<
|
||
|
|
private_unpack_type,
|
||
|
|
typename unpack_impl_result<Sequence>::type
|
||
|
|
>
|
||
|
|
{};
|
||
|
|
#endif
|
||
|
|
template<class Sequence, class=void>
|
||
|
|
struct is_unpackable_impl
|
||
|
|
: std::true_type
|
||
|
|
{
|
||
|
|
#if BOOST_HOF_CHECK_UNPACK_SEQUENCE
|
||
|
|
static_assert(is_proper_sequence<Sequence>::value,
|
||
|
|
"Unpack is invalid for this sequence. The function used to unpack this sequence does not invoke the function."
|
||
|
|
);
|
||
|
|
#endif
|
||
|
|
};
|
||
|
|
|
||
|
|
template<class Sequence>
|
||
|
|
struct is_unpackable_impl<Sequence, typename detail::holder<
|
||
|
|
typename unpack_sequence<Sequence>::not_unpackable
|
||
|
|
>::type>
|
||
|
|
: std::false_type
|
||
|
|
{};
|
||
|
|
|
||
|
|
}
|
||
|
|
|
||
|
|
template<class Sequence>
|
||
|
|
struct is_unpackable
|
||
|
|
: detail::is_unpackable_impl<
|
||
|
|
typename std::remove_cv<typename std::remove_reference<Sequence>::type>::type
|
||
|
|
>
|
||
|
|
{
|
||
|
|
#if BOOST_HOF_CHECK_UNPACK_SEQUENCE
|
||
|
|
typedef detail::is_unpackable_impl<
|
||
|
|
typename std::remove_cv<typename std::remove_reference<Sequence>::type>::type
|
||
|
|
> base;
|
||
|
|
|
||
|
|
typedef std::conditional<base::value, detail::is_proper_sequence<Sequence>, std::true_type> check;
|
||
|
|
static_assert(check::type::value,
|
||
|
|
"Unpack is invalid for this sequence. The function used to unpack this sequence does not invoke the function."
|
||
|
|
);
|
||
|
|
#endif
|
||
|
|
};
|
||
|
|
|
||
|
|
}} // namespace boost::hof
|
||
|
|
|
||
|
|
#endif
|