Edit: /usr/include/boost/hana/slice.hpp (3407B)
/*!
@file
Defines `boost::hana::slice` and `boost::hana::slice_c`.
@copyright Louis Dionne 2013-2017
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_SLICE_HPP
#define BOOST_HANA_SLICE_HPP
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
BOOST_HANA_NAMESPACE_BEGIN
//! @cond
template
constexpr auto slice_t::operator()(Xs&& xs, Indices&& indices) const {
using S = typename hana::tag_of::type;
using Slice = BOOST_HANA_DISPATCH_IF(slice_impl,
hana::Sequence::value &&
hana::Foldable::value
);
#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
static_assert(hana::Sequence::value,
"hana::slice(xs, indices) requires 'xs' to be a Sequence");
static_assert(hana::Foldable::value,
"hana::slice(xs, indices) requires 'indices' to be Foldable");
#endif
return Slice::apply(static_cast(xs), static_cast(indices));
}
//! @endcond
namespace detail {
template
struct take_arbitrary {
Xs& xs;
using S = typename hana::tag_of::type;
template
constexpr auto operator()(N const& ...) const {
return hana::make(hana::at_c(xs)...);
}
};
}
template
struct slice_impl> : default_ {
template
static constexpr auto from_offset(Xs&& xs, std::index_sequence) {
return hana::make(hana::at_c(static_cast(xs))...);
}
template
static constexpr auto apply(Xs&& xs, hana::range const&) {
return slice_impl::from_offset(
static_cast(xs), std::make_index_sequence{}
);
}
//! @todo
//! Since we have the right to specify the same index more than once,
//! we can't move from the elements of the source sequence even if it
//! is a temporary object: we could end up double-moving. Perhaps it
//! would be possible to determine the indices from which we can move
//! without incurring a too large compile-time penalty?
template
static constexpr auto apply(Xs const& xs, Indices const& indices) {
return hana::unpack(indices, detail::take_arbitrary{xs});
}
};
template
struct slice_c_t {
template
constexpr auto operator()(Xs&& xs) const {
return hana::slice(static_cast(xs),
hana::range_c);
}
};
BOOST_HANA_NAMESPACE_END
#endif // !BOOST_HANA_SLICE_HPP